14277-97-5VZFRNCSOCOPNDB-AOKDLOFSSA-NVZFRNCSOCOPNDB-AOKDLOFSSA-N
L-Domoic acid(2S,3S,4R,5'R)-2-Carboxy-4-(5'-carboxy-1'-methyl-1Z,3E-hexadienyl)-3-pyrrolidineacetic acid
DTXSID20274180GO:0008328ionotropic glutamate receptor complexGO:0017146NMDA selective glutamate receptor complexCHEBI:39124calcium ionGO:0004970ionotropic glutamate receptor activityGO:0004972NMDA glutamate receptor activityGO:0007612learningGO:0007613memoryGO:0006816calcium ion transportGO:0099536synaptic signaling1increased2decreasedDomoic acid2016-11-29T18:42:132016-11-29T18:42:13WCS_7227Drosophila melanogaster10116Rattus norvegicus976298Primates sp. BOLD:AAA0001WCS_9606human10095mice10090mouse10116ratWCS_7955zebrafishWCS_7227fruit flyWCS_160004gastropodsWCS_9606humans9685cat9606Homo sapiens10090Mus musculusBinding of agonist, Ionotropic glutamate receptorsBinding of agonist, Ionotropic glutamate receptorsMolecular<p>The MIE of this AOP can be triggered by direct binding of an agonist to NMDARs or indirectly through initial activation of KA/AMPARs. Indeed, binding of agonist to KA/AMPARs results in ion influx (Na+ and a small efflux of K+) and glutamate release from excitatory synaptic vesicles causing depolarization of the postsynaptic neuron (Dingledine et al. 1999). Upon this depolarization the Mg2+ block is removed from the pore of NMDARs, allowing sodium, potassium, and importantly, calcium ions to enter into a cell. At positive potentials NMDARs then show maximal permeability (i.e., large outward currents can be observed under these circumstances). Due to the time needed for the Mg2+ removal, NMDARs activate more slowly, having a peak conductance long after the KA/AMPAR peak conductance takes place. It is important to note that NMDARs conduct currents only when Mg2+ block is relieved, glutamate is bound, and the postsynaptic neuron is depolarized. For this reason the NMDA receptors act as “coincidence detectors” and play a fundamental role in the establishment of Hebbian synaptic plasticity which is considered the physiological correlate of associative learning (Daoudal and Debanne, 2003; Glanzman, 2005). Post-synaptic membrane depolarization happens almost always through activation of KA/AMPARs (Luscher and Malenka, 2012). Therefore, a MIE of this AOP is defined as binding of an agonist to these three types of ionotropic receptors (KA/AMPA and NMDA) that can result in a prolonged overactivation of NMDARs through (a) direct binding of an agonist or (b) indirect, mediated through initial KA/AMPARs activation. The excitotoxic neuronal cell death, triggered by sustained NMDARs overactivation in the hippocampus and/or cortex leads to the impaired learning and memory, defined as the adverse outcome (AO) of this AOP.
</p><p><br />
<b>Biological state:</b>
L-glutamate (Glu) is a neurotransmitter with important role in the regulation of brain development and maturation processes. Two major classes of Glu receptors, ionotropic and metabotropic, have been identified. Due to its physiological and pharmacological properties, Glu activates three classes of ionotropic receptors named: α-amino-3-hydroxy-5-methyl-4-isoazolepropionic acid (AMPA receptors), 2-carboxy-3-carboxymethyl-4-isopropenylpyrrolidine (kainate receptors) and N-methyl-D-aspartate (NMDA receptors, NMDARs), which transduce the postsynaptic signal. Ionotropic glutamate receptors are integral membrane proteins formed by four large subunits that compose a central ion channel pore. In case of NMDA receptors, two NR1 subunits are combined with either two NR2 (NR2A, NR2B, NR2C, NR2D) subunits and less commonly are assembled together with a combination of NR2 and NR3 (A, B) subunits (reviewed in Traynelis et al., 2010). To be activated NMDA receptors require simultaneous binding of both glutamate to NR2 subunits and of glycine to either NR1 or NR3 subunits that provide the specific binding sites named extracellular ligand-binding domains (LBDs). Apart from LBDs, NMDA receptor subunits contain three more domains that are considered semiautonomous: 1) the extracellular amino-terminal domain that plays important role in assembly and trafficking of these receptors; 2) the transmembrane domain that is linked with LBD and contributes to the formation of the core of the ion channel and 3) the intracellular carboxyl-terminal domain that influences membrane targeting, stabilization, degradation and post-translation modifications.
</p><p><br />
<b>Biological compartments:</b>
The genes of the NMDAR subunits are expressed in various tissues and are not only restricted to the nervous system. The level of expression of these receptors in neuronal and non-neuronal cells depends on: transcription, chromatin remodelling, mRNA levels, translation, stabilization of the protein, receptor assembly and trafficking, energy metabolism and numerous environmental stimuli (reviewed in Traynelis et al., 2010).
In hippocampus region of the brain, NR2A and NR2B are the most abundant NR2 family subunits. NR2A-containing NMDARs are mostly expressed synaptically, while NR2B-containing NMDARs are found both synaptically and extrasynaptically (Tovar and Westbrook, 1999).
</p><p><br />
<b>General role in biology:</b>
NMDA receptors, when compared to the other Glu receptors, are characterized by higher affinity for Glu, slower activation and desensitisation kinetics, higher permeability for calcium (Ca2+) and susceptibility to potential-dependent blockage by magnesium ions (Mg2+). NMDA receptors are involved in fast excitatory synaptic transmission and neuronal plasticity in the central nervous system (CNS). Functions of NMDA receptors:
</p><p>1. They are involved in cell signalling events converting environmental stimuli to genetic changes by regulating gene transcription and epigenetic modifications in neuronal cells (Cohen and Greenberg, 2008).
</p><p>2. In NMDA receptors, the ion channel is blocked by extracellular Mg2+ and Zn2+ ions, allowing the flow of Na+ and Ca2+ ions into the cell and K+ out of the cell which is voltage-dependent. Ca2+ flux through the NMDA receptor is considered to play a critical role in pre- and post-synaptic plasticity, a cellular mechanism important for learning and memory (Barria and Malinow, 2002).
</p><p>3. The NMDA receptors have been shown to play an essential role in the strengthening of synapses and neuronal differentiation, through long-term potentiation (LTP), and the weakening of synapses, through long-term depression (LTD). All these processes are implicated in the memory and learning function (Barria and Malinow, 2002).
</p><p><em>
Methods that have been previously reviewed and approved by a recognized authority should be included in the Overview section above.
All other methods, including those well established in the published literature, should be described here.
Consider the following criteria when describing each method:
1. Is the assay fit for purpose?
2. Is the assay directly or indirectly (i.e. a surrogate) related to a key event relevant to the final
adverse effect in question?
3. Is the assay repeatable?
4. Is the assay reproducible?
</em>
</p><p>1. Ex vivo: The most common assay used is the NMDA receptor (MK801 site) radioligand competition binding assay (Reynolds and Palmer, 1991; Subramaniam and McGonigle, 1991; <a rel="nofollow" target="_blank" class="external free" href="http://pdsp.med.unc.edu/UNC-CH%20Protocol%20Book.pdf">http://pdsp.med.unc.edu/UNC-CH%20Protocol%20Book.pdf</a>; <a rel="nofollow" target="_blank" class="external free" href="http://www.currentprotocols.com/WileyCDA/CPUnit/refId-ph0120.html">http://www.currentprotocols.com/WileyCDA/CPUnit/refId-ph0120.html</a>). This assay
is based on the use of the most potent and specific antagonist of this receptor, MK801 that is used to detect and differentiate agonists and antagonists (competitive and non-competitive) that bind to this specific site of the receptor. Also radioligand competition binding assay can be performed using D, L-(E)-2-amino-4-[3H]-propyl-5-phosphono-3-pentenoic acid ([3H]-CGP 39653), a high affinity selective antagonist at the glutamate site of NMDA receptor, which is a quantitative autoradiography technique (Mugnaini et al., 1996). D-AP5, a selective N-methyl-D-aspartate (NMDA) receptor antagonist that competitively inhibits the glutamate binding site of NMDA receptors, can be studied by evoked electrical activity measurements. AP5 has been widely used to study the activity of NMDA receptors particularly with regard to researching synaptic plasticity, learning, and memory (Evans et al.,1982; Morris, 1989). The saturation binding of radioligands are used to measure the affinity (Kd) and density (Bmax) of kainate and AMPA receptors in striatum, cortex and hippocampus (Kürschner et al., 1998).
</p><p>2. In silico: The prediction of NMDA receptor targeting is achievable by combining database mining, molecular docking, structure-based pharmacophore searching, and chemical similarity searching methods together (Neville and Lytton, 1999; Mazumder Borah, 2014)
</p><hr /> The major determinants for ligand e.g. for both co-agonist glycine binding and L-glutamate binding are well conserved between species from lower organism to mammals (reviewed in Xia and Chiang, 2009). PCR analysis, cloning and subsequent sequencing of the seal lion NMDA receptors showed 80% homology to those from rats, but more than 95% homologus to those from dogs (Gill et al., 2010).CL:0000540neuronHighHighHighHighHigh<p><br />
(for Abstract and MIE)
</p><p>Barenberg P, Strahlendorf H, Strahlendorf., Hypoxia induces an excitotoxic-type of dark cell degeneration in cerebellar Purkinje neurons. J. Neurosci Res. 2001, 40(3): 245-54.
</p><p>Barria A, Malinow R. (2002) Subunit-specific NMDA receptor trafficking to synapses. Neuron 35: 345-353.
Cohen S, Greenberg ME. (2008) Communication between the synapse and the nucleus in neuronal development, plasticity, and disease. Ann Rev Cell Dev Biol 24: 183-209.
</p><p>Berman F.W. and T. F. Murray, “Domoic acid neurotoxicity in cultured cerebellar granule neurons is mediated predominantly by NMDA receptors that are activated as a consequence of excitatory amino acid release,” Journal of Neurochemistry, 1997, 69: 693–703.
</p><p>Berman W.F., K. T. LePage, and T. F. Murray, Domoic acid neurotoxicity in cultured cerebellar granule neurons is controlled preferentially by the NMDA receptor Ca2+ influx pathway,” Brain Research, 2002, 924: 20–29.
</p><p>Cohen S, Greenberg ME. (2008) Communication between the synapse and the nucleus in neuronal development, plasticity, and disease. Ann Rev Cell Dev Biol 24: 183-209.
</p><p>Daoudal G, Debanne D, Long-term plasticity of intrinsic excitability: learning rules and mechanisms. Learn Mem., 2003, 10(6):456-65.
</p><p>Dingledine R, Borges K, Bowie D, Traynelis SF., The glutamate receptor ion channels. Pharmacol Rev., 1999, 51: 7–61.
</p><p>Evans, R.H., Francis, A.A., Jones, A.W., et al., The Effects of a Series of ω-Phosphonic α-Carboxylic Amino Acids on Electrically Evoked and Excitant Amino Acid-Induced Responses in Isolated Spinal Cord Preparations. Br J Pharmac., 1982, 75: 65-75.
</p><p>Gill S, Goldstein T, Situ D, Zabka TS, Gulland FM, Mueller RW., Cloning and characterization of glutamate receptors in Californian sea lions (Zalophus californianus). Mar Drugs, 2010, 8: 1637-1649.
</p><p>Glanzman DL., Associative learning: Hebbian flies. Curr Biol., 2005, 7: 15(11):R416-9.
</p><p>Kürschner VC, Petruzzi RL, Golden GT, Berrettini WH, Ferraro TN., Kainate and AMPA receptor binding in seizure-prone and seizure-resistant inbred mouse strains. Brain Res. 1998, 5: 780-788.
</p><p>Lantz SR, Mack CM, Wallace K, Key EF, Shafer TJ, Casida JE., Glufosinate binds N-methyl-D-aspartate receptors and increases neuronal network activity in vitro. Neurotoxicology, 2014, 45: 38-47.
</p><p>Lefebvre KA, Robertson A., Domoic acid and human exposure risks: a review.Toxicon. 2010, 56: 218-30.
</p><p>Luscher C. and Robert C. Malenka., NMDA Receptor-Dependent Long-Term Potentiation and Long-Term Depression (LTP/LTD). Cold Spring Harb Perspect Biol 2012, 4: a005710.
</p><p>Matsumura N, Takeuchi C., Hishikawa K, Fujii T, Nakaki T., Glufosinate ammonium induces convulsion through N-methyl-D-aspartate receptors in mice. Neurosci Lett. 2001, 304: 123-5.
</p><p>Mazumder MK, Borah A. Piroxicam inhibits NMDA receptor-mediated excitotoxicity through allosteric inhibition of the GluN2B subunit: an in silico study elucidating a novel mechanism of action of the drug. Med Hypotheses. 2014, 83(6): 740-6.
</p><p>Mehta A, Prabhakar M, Kumar P, Deshmukh R, Sharma PL. Excitotoxicity: bridge to various triggers in neurodegenerative disorders. Eur J Pharmacol. 2013, 698: 6-18.
</p><p>Morris, RJ. Synaptic Plasticity and Learning: Selective Impairment of Learning in Rats and Blockade of Long-Term Potentiation in vivo by the N-Methyl-D-Aspartate Receptor Antagonist AP5. J Neurosci., 1989, 9: 3040-3057.
</p><p>Mugnaini M, van Amsterdam FT, Ratti E, Trist DG, Bowery NG. Regionally different N-methyl-D-aspartate receptors distinguished by ligand binding and quantitative autoradiography of [3H]-CGP 39653 in rat brain.British Journal of Pharmacology, 1996, 119: 819–828.
</p><p>Neville KR, Lytton WW. Potentiation of Ca2+ influx through NMDA channels by action potentials: a computer model. Neuroreport., 1999, 10(17): 3711-6.
</p><p>Pulido OM., Domoic acid toxicologic pathology: a review. Mar Drugs., 2008, 6: 180-219.
</p><p><br />
Reynolds IJ, Palmer AM. Regional variations in [3H]MK801 binding to rat brain N-methyl-D-aspartate receptors. J Neurochem. 1991, 56(5):1731-40.
</p><p>Subramaniam S, McGonigle P. Quantitative autoradiographic characterization of the binding of (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5, 10-imine ([3H]MK-801) in rat brain: regional effects of polyamines. J Pharmacol Exp Ther. 1991, 256(2): 811-9.
</p><p>Schrattenholz A, Soskic V., NMDA receptors are not alone: dynamic regulation of NMDA receptor structure and function by neuregulins and transient cholesterol-rich membrane domains leads to disease-specific nuances of glutamate-signalling.Curr Top Med Chem., 2006, 6(7):663-86.
</p><p>Tovar KR, Westbrook GL. (1999) The incorporation of NMDA receptors with a distinct subunit composition at nascent hippocampal synapses in vitro. J Neurosci. 19: 4180–4188.
</p><p>Traynelis S, Wollmuth LP, McBain CJ, Menniti FS, Vance KM, Ogden KK, Hansen KB, Yuan H, Myers SJ, Dingledine R. Glutamate receptor ion channels: structure, regulation, and function. Pharmacol Rev., 2010, 62: 405-496.
</p><p>Watanabe KH, Andersen ME, Basu N, Carvan MJ 3rd, Crofton KM, King KA, Suñol C, Tiffany-Castiglioni E, Schultz IR. Defining and modeling known adverse outcome pathways: Domoic acid and neuronal signaling as a case study. Environ Toxicol Chem., 2011, 30: 9-21.
</p><p>Xia S, Chiang AS. NMDA Receptors in Drosophila. In: Van Dongen AM, editor. Biology of the NMDA Receptor. Boca Raton (FL): CRC Press; 2009. Chapter 10. Available from: <a rel="nofollow" target="_blank" class="external free" href="http://www.ncbi.nlm.nih.gov/books/NBK5286/">http://www.ncbi.nlm.nih.gov/books/NBK5286/</a>
</p><p>Retrieved from <a rel="nofollow" target="_blank" class="external free" href="https://aopkb.org/aopwiki/index.php/?oldid=27027">https://aopkb.org/aopwiki/index.php/?oldid=27027</a>
</p>2016-11-29T18:41:272017-09-16T10:15:07Overactivation, NMDARsOveractivation, NMDARsCellular<p><strong>Biological state:</strong> Please see MIE <a href="/wiki/index.php/Event:201" title="Event:201"> NMDARs, Binding of antagonist</a></p>
<p><strong>Biological compartments:</strong> Please see MIE <a href="/wiki/index.php/Event:201" title="Event:201"> NMDARs, Binding of antagonist</a></p>
<p><strong>General role in biology:</strong> Please see MIE <a href="/wiki/index.php/Event:201" title="Event:201"> NMDARs, Binding of antagonist</a></p>
<p>The above chapters belong to the AOP entitled: <em>Chronic binding of antagonist to N-methyl-D-aspartate receptors (NMDARs) during brain development induces impairment of learning and memory abilities</em> since the general characteristic of the NMDA receptor biology is the same for both AOPs.</p>
<p>Additional text, specific for this AOP:</p>
<p>At resting membrane potentials, NMDA receptors are inactive. Depending on the specific impulse train received, the NMDA receptor activation triggers long term potentiation (LTP) or long-term depression (LTD) (Malenka and Bear, 2004; Luscher and Malenka, 2012). LTP (the opposing process to LTD) is the long-lasting increase of synaptic strength. For LTP induction both pre- and postsynaptic neurons need to be active at the same time because the postsynaptic neuron must be depolarized when glutamate is released from the presynaptic bouton to fully relieve the Mg2+ block of NMDARs that prevents ion flows through it. Sustained activation of AMPA or KA receptors by, for instance, a train of impulses arriving at a pre-synaptic terminal, depolarizes the post-synaptic cell, releasing Mg2+ inhibition and thus allowing NMDA receptor activation. Unlike GluA2-containing AMPA receptors, NMDA receptors are permeable to calcium ions as well as being permeable to other ions. Thus NMDA receptor activation leads to a calcium influx into the post-synaptic cells, a signal that is instrumental in the activation of a number of signalling cascades (<em>Calcium-dependent processes are describe in Key Event Calcium influx, increased</em>). Postsynaptic Ca2+ signals of different amplitudes and durations are able to induce either LPT or LTD.</p>
<p>Conversely to LTP, LTD is induced by repeated activation of the presynaptic neuron at low frequencies without postsynaptic activity (Luscher and Malenka, 2012). Therefore, under physiological conditions LTD is one of several processes that serves to selectively weaken specific synapses in order to make constructive use of synaptic strengthening caused by LTP. This is necessary because, if allowed to continue increasing in strength, synapses would ultimately reach a ceiling level of efficiency, which would inhibit the encoding of new information (Purves, 2008).</p>
<p>LTD is an activity-dependent reduction in the efficacy of neuronal synapses lasting hours or longer following a long patterned stimulus. It has also been found to occur in different types of neurons however, the most common neurotransmitter involved in LTD is L-glutamate that acts on the NMDARs, AMPAR, KARs and metabotropic glutamate receptors (mGluRs). It can result from strong synaptic stimulation (as occurs e.g. in the cerebellar Purkinje cells) or from persistent weak synaptic stimulation (as in the hippocampus) resulting mainly from a decrease in postsynaptic AMPA receptor density, although a decrease in presynaptic neurotransmitter release may also play a role. Moreover, cerebellar LTD has been hypothesized to be important for motor learning and hippocampal LTD may be important for the clearing of old memory traces (Nicholls et al., 2008; Mallere et al., 2010). The main molecular mechanism underlying-LTD is the phosphorylation of AMPA glutamate receptors and their synaptic elimination (Ogasawara et al., 2008).</p>
<p>It is now commonly understood in the field of spine morphology that long lasting NMDAR-dependent LTD causes dendritic spine shrinkage, reduces number of synaptic AMPA receptors (Calabrese et al., 2014), possibly leading to synaptic dysfunction, contributing to decreased neuronal network function and impairment of learning and memory processes.</p>
<p>Additional text, specific for the AOP “Acetylcholinesterase inhibition leading to neurodegeneration”:</p>
<p> Seizures caused by cholinesterase dependent mechanisms result in an excess of glutamate release that activates the NMDA receptors. As a result, intracellular Ca2+ levels at the postsynaptic neuron can overload the calcium-control mechanisms, activating without control all the calcium-dependent enzymes (proteases, lipases…) (Deshpande et al., 2014; Garcia-Reyero et al., 2016). In cases of strong acetylcholinesterase inhibition of the CNS, the NMDAR overactivation initiated by cholinergic mechanisms can result, after the initial seizure activity (focal seizure), in the development of status epilepticus. This key event separates the initial toxicity, driven by cholinergic activity, from the secondary toxicity, which is cholinergic independent (McDonough and Shih, 1997).</p>
<p><!--[endif]----><!--[endif]----></p>
<p><em>Methods that have been previously reviewed and approved by a recognized authority should be included in the Overview section above. All other methods, including those well established in the published literature, should be described here. Consider the following criteria when describing each method: 1. Is the assay fit for purpose? 2. Is the assay directly or indirectly (i.e. a surrogate) related to a key event relevant to the final adverse effect in question? 3. Is the assay repeatable? 4. Is the assay reproducible? </em></p>
<p>No OECD methods are available to measure the activation state of NMDA receptors.</p>
<p>The measurement of the activation or the inhibition of NMDA receptors is done indirectly by recording the individual ion channels that are selective to Na+, K+ and Ca2+ by the patch clamp technique. This method relies on lack of measurable ion flux when NMDA ion channel is closed, whereas constant channel specific conductance is recorded at the open state of the receptor (Blanke and VanDongen, 2009). Furthermore, this method is based on the prediction that activation or inhibition of an ion channel results from an increase in the probability of being in the open or closed state, respectively (Ogdon and Stanfield, 2009; Zhao et al., 2009).</p>
<p>The whole-cell patch clamp recording techniques have also been used to study synaptically-evoked NMDA receptor-mediated excitatory or inhibitory postsynaptic currents (EPSCs and IPSCs, respectively) in brain slices and neuronal cells, allowing the evaluation of the activated or inhibited state of the receptor.</p>
<p>Microelectrode array (MEA) recordings are used to measure mainly spontaneous network activity of cultured neurons (Keefer et al., 2001, Gramowski et al., 2000 and Gopal, 2003; Johnstone et al., 2010). However, using specific agonists and antagonists of a receptor, including NMDAR, MEA technology can be used to measure evoked activity, including glutamatergic receptor function (Lantz et al., 2014). For example it has been shown that MEA-coupled neuronal cortical networks are very sensitive to pharmacological manipulation of the excitatory ionotropic glutamatergic transmission (Frega et al., 2012). MEAs can also be applied in higher throughput platforms to facilitate screening of numerous chemical compounds (McConnell et al., 2012).</p>
<p>Excessive excitability can be also measured directly by evaluating the level of the extracellular glutamate using the enzyme-based microelectrode arrays. This technology is capable of detecting glutamate in vivo, to assess the effectiveness of hyperexcitability modulators on glutamate release in brain slices. Using glutamate oxidase coated ceramic MEAs coupled with constant voltage amperometry, it is possible to measure resting glutamate levels and synaptic overflow of glutamate after K(+) stimulation in brain slices (Quintero et al., 2011).</p>
<p>Neuronal network function can be also measured using optical detection of neuronal spikes both in vivo and in vitro (Wilt et al., 2013).</p>
<p>Drebrin immunocytochemistry: drebrin, a major actin-filament-binding protein localized in mature dendritic spines is a target of calpain mediated proteolysis under excitotoxic conditions induced by the overactivation of NMDARs. In cultured rodent neurons, degradation of drebrin was confirmed by the detection of proteolytic fragments, as well as a reduction in the amount of full-length drebrin. The NMDA-induced degradation of drebrin in mature neurons occurres concomitantly with a loss of f-actin. Biochemical analyses using purified drebrin and calpain revealed that calpain degraded drebrin directly in vitro. These findings suggest that calpain-mediated degradation of drebrin is mediated by excitotoxicity, regardless of whether they are acute or chronic. Drebrin (A and E) regulates the synaptic clustering of NMDARs. Therefore, degradation of drebrin can be used as a readout for excitotoxicity induced by NMDAR overactivation. Degradation of drebrin can be evaluated quantitatively by Western blot analysis (mRNA evel) or by immunocytochemistry (at protein level) (Chimura et al., 2015: Sekino et al., 20069.</p>
<p>NMDAR overactivation-induced long lasting LTD can be measured by the dendritic spine shrinkage by quantification of cofilin and phospho-cofilin in neurons expressing eGFP and combined with immunocytochemical techniques (Calabrese et al., 2014).</p>
<p>It is important to note that in invertebrates the glutamatergic synaptic transmission has an inhibitory and not an excitatory role like in vertebrates. This type of neurotransmission is mediated by glutamate-gated chloride channels that are members of the ‘cys-loop’ ligand-gated anion channel superfamily found only in invertebrates. The subunits of glutamate-activated chloride channel have been isolated from C. elegans and from Drosophila (Blanke and VanDongen, 2009).</p>
CL:0000540neuronHighHighHighHigh<p><br />
Blanke ML, VanDongen AMJ., Activation Mechanisms of the NMDA Receptor. In: Van Dongen AM, editor. Biology of the NMDA Receptor. Boca Raton (FL): CRC Press; 2009, Chapter 13. Available from: <a class="external free" href="http://www.ncbi.nlm.nih.gov/books/NBK5274/" rel="nofollow" target="_blank">http://www.ncbi.nlm.nih.gov/books/NBK5274/</a>.</p>
<p>Calabrese B, Saffin JM, Halpain S. Activity-dependent dendritic spine shrinkage and growth involve downregulation of cofilin via distinct mechanisms. PLoS One., 2014, 16;9(4):e94787.</p>
<p>Chimura T., Launey T., Yoshida N.,Calpain-Mediated Degradation of Drebrin by Excitotoxicity In vitro and In vivo PLOS ONE, 2015, |DOI:10.1371/journal.pone.0125119.</p>
<p>Deshpande, L. S., D. S. Carter, K. F. Phillips, R. E. Blair and R. J. DeLorenzo (2014), "Development of status epilepticus, sustained calcium elevations and neuronal injury in a rat survival model of lethal paraoxon intoxication”, <em>NeuroToxicology</em> <strong>44</strong>: 17-26. DOI: 10.1016/j.neuro.2014.04.006.</p>
<p>Frega M, Pasquale V, Tedesco M, Marcoli M, Contestabile A, Nanni M, Bonzano L, Maura G, Chiappalone M., Cortical cultures coupled to micro-electrode arrays: a novel approach to perform in vitro excitotoxicity testing. Neurotoxicol Teratol. 2012: 34(1):116-27.</p>
<p>Garcia-Reyero, N., L. Escalon, E. Prats, M. Faria, A. M. V. M. Soares and D. Raldúa (2016), "Targeted Gene Expression in Zebrafish Exposed to Chlorpyrifos-Oxon Confirms Phenotype-Specific Mechanisms Leading to Adverse Outcomes”, <em>Bulletin of Environmental Contamination and Toxicology</em> <strong>96</strong>(6): 707-713. DOI: 10.1007/s00128-016-1798-3.</p>
<p>Gopal K., Neurotoxic effects of mercury on auditory cortex networks growing on microelectrode arrays: a preliminary analysis. Neurotoxicol Teratol., 2003, 25: 69-76.</p>
<p>Gramowski A, Schiffmann D, Gross GW., Quantification of acute neurotoxic effects of trimethyltin using neuronal networks cultures on microelectrode arrays. Neurotoxicology, 2000, 21: 331-342.</p>
<p>Johnstone AFM, Gross GW, Weiss D, Schroeder O, Shafer TJ.,Use of microelectrode arrays for neurotoxicity testing in the 21st century Neurotoxicology, 2000, 31: 331-350.</p>
<p>Keefer E, Norton S, Boyle N, Talesa V, Gross G., Acute toxicity screening of novel AChE inhibitors using neuronal networks on microelectrode arrays. Neurotoxicology, 2001, 22: 3-12.</p>
<p>Lantz SR, Mack CM, Wallace K, Key EF, Shafer TJ, Casida JE. Glufosinate binds N-methyl-D-aspartate receptors and increases neuronal network activity in vitro. Neurotoxicology. 2014, 45:38-47.</p>
<p>Luscher C. and Malenka R.C., NMDA Receptor-Dependent Long-Term Potentiation and Long-Term Depression (LTP/LTD). Cold Spring Harb Perspect Biol., 2012, 4:a005710.</p>
<p>Malenka RC, Bear MF., LTP and LTD: An embarrassment of riches. Neuron, 2004, 44: 5–21.</p>
<p>Malleret G, Alarcon JM, Martel G, Takizawa S, Vronskaya S, Yin D, Chen IZ, Kandel ER, Shumyatsky GP., Bidirectional regulation of hippocampal long-term synaptic plasticity and its influence on opposing forms of memory". J Neurosci., 2010, 30 (10): 3813–25.</p>
<p>McConnell ER, McClain MA, Ross J, LeFew WR, Shafer TJ., Evaluation of multi-well microelectrode arrays for neurotoxicity screening using a chemical training set Neurotoxicology, 2012, 33: 1048-1057.</p>
<p>McDonough, J. H., Jr. and T. M. Shih (1997), "Neuropharmacological mechanisms of nerve agent-induced seizure and neuropathology”, <em>Neurosci Biobehav Rev</em> <strong>21</strong>(5): 559-579.</p>
<p>Nicholls RE, Alarcon JM, Malleret G, Carroll RC, Grody M, Vronskaya S, Kandel ER., Transgenic mice lacking NMDAR-dependent LTD exhibit deficits in behavioral flexibility". Neuron, 2008, 58 (1): 104–17.</p>
<p>Ogasawara H, Doi T, Kawato M. Systems biology perspectives on cerebellar long-term depression. Neurosignals, 2008, 16 (4): 300–17.</p>
<p>Ogdon D, Stanfield P., Patch clamp techniques for single channel and whole-cell recording. Chapter 4, pages 53-78, (<a class="external free" href="http://www.utdallas.edu/~tres/microelectrode/microelectrodes_ch04.pdf" rel="nofollow" target="_blank">http://www.utdallas.edu/~tres/microelectrode/microelectrodes_ch04.pdf</a>).</p>
<p>Paradiso MA, Bear MF, Connors BW., Neuroscience: exploring the brain. 2007, Hagerstwon, MD: Lippincott Williams & Wilkins. p. 718. <a class="internal mw-magiclink-isbn" href="/wiki/index.php/Special:BookSources/0781760038">ISBN 0-7817-6003-8</a>.</p>
<p>Purves D., Neuroscience (4th ed.). Sunderland, Mass: Sinauer., 2008, pp. 197–200. <a class="internal mw-magiclink-isbn" href="/wiki/index.php/Special:BookSources/0878936971">ISBN 0-87893-697-1</a>.</p>
<p>Sekino Y, Tanaka S, Hanamura K, Yamazaki H, Sasagawa Y, Xue Y, Hayashi K, Shirao T., Activation of N-methyl-D-aspartate receptor induces a shift of drebrin distribution: disappearance from dendritic spines and appearance in dendritic shafts. Mol Cell Neurosci. 2006, 31(3):493-504.</p>
<p>Quintero JE, Pomerleau F, Huettl P, Johnson KW, Offord J, Gerhardt GA. 2011. Methodology for rapid measures of glutamate release in rat brain slices using ceramic-based microelectrode arrays: basic characterization and drug pharmacology. Brain Res.2011, 1401:1-9.</p>
<p>Wilt BA, Fitzgerald JE, Schnitzer MJ., Photon shot noise limits on optical detection of neuronal spikes and estimation of spike timing. Biophys J. 2013, 8; 104(1):51-62.</p>
<p>Zhao Y, Inayat S, Dikin DA, Singer JH, Ruoff RS, Troy JB., Patch clamp techniques: review of the current state of art and potential contributions from nanoengineering. Proc. IMechE 222, Part N: J. Nanoengineering and Nanosystems, 2009, 149. DOI: 10.1243/17403499JNN149.</p>
2016-11-29T18:41:242023-01-04T18:39:50Loss of drebrinLoss of drebrinCellular2022-12-11T21:04:592022-12-11T21:04:59Synaptic dysfunctionDysfunctional synapsesOrgan2021-10-26T06:58:462023-01-04T18:47:00Impairment, Learning and memoryImpairment, Learning and memoryIndividual<p> </p>
<p>Learning can be defined as the process by which new information is acquired to establish knowledge by systematic study or by trial and error (Ono, 2009). Two types of learning are considered in neurobehavioral studies: a) associative learning and b) non-associative learning. Associative learning is based on making associations between different events. In associative learning, a subject learns the relationship among two different stimuli or between the stimulus and the subject’s behaviour. On the other hand, non-associative learning can be defined as an alteration in the behavioural response that occurs over time in response to a single type of stimulus. Habituation and sensitization are some examples of non-associative learning.</p>
<p>The memory formation requires acquisition, retention and retrieval of information in the brain, which is characterised by the non-conscious recall of information (Ono, 2009). There are three main categories of memory, including sensory memory, short-term or working memory (up to a few hours) and long-term memory (up to several days or even much longer).</p>
<p>Learning and memory depend upon the coordinated action of different brain regions and neurotransmitter systems constituting functionally integrated neural networks (D’Hooge and DeDeyn, 2001). Among the many brain areas engaged in the acquisition of, or retrieval of, a learned event, the hippocampal-based memory systems have received the most study. For example, the hippocampus has been shown to be critical for spatial-temporal memory, visio-spatial memory, verbal and narrative memory, and episodic and autobiographical memory (Burgess et al., 2000; Vorhees and Williams, 2014). However, there is substantial evidence that fundamental learning and memory functions are not mediated by the hippocampus alone but require a network that includes, in addition to the hippocampus, anterior thalamic nuclei, mammillary bodies cortex, cerebellum and basal ganglia (Aggleton and Brown, 1999; Doya, 2000; Mitchell et al., 2002, Toscano and Guilarte, 2005; Gilbert et al., 2006, 2016). Thus, damage to variety of brain structures can potentially lead to impairment of learning and memory. The main learning areas and pathways are similar in rodents and primates, including man (Eichenbaum, 2000; Stanton and Spear, 1990).While the prefrontal cortex and frontostriatal neuronal circuits have been identified as the primary sites of higher-order cognition in vertebrates, invertebrates utilize paired mushroom bodies, shown to contain ~300,000 neurons in honey bees (Menzel, 2012; Puig et al., 2014).</p>
<p>For the purposes of this KE (AO), impaired learning and memory is defined as an organism’s inability to establish new associative or non-associative relationships, or sensory, short-term or long-term memories which can be measured using different behavioural tests described below.</p>
<p><strong>In laboratory animals:</strong> in rodents, a variety of tests of learning and memory have been used to probe the integrity of hippocampal function. These include tests of spatial learning like the radial arm maze (RAM), the Barnes maze, <span style="color:#3498db">Hebb-Williams maze</span>, passive avoidance and Spontaneous alternation and most commonly, the Morris water maze (MWM). Test of novelty such as novel object recognition, and fear based context learning are also sensitive to hippocampal disruption. Finally, trace fear conditioning which incorporates a temporal component upon traditional amygdala-based fear learning engages the hippocampus. A brief description of these tasks follows.</p>
<p>1) RAM, Barnes, MWM, <span style="color:#3498db">Hebb-Williams maze </span>are examples of spatial tasks, animals are required to learn the location of a food reward (RAM); an escape hole to enter a preferred dark tunnel from a brightly lit open field area (Barnes maze), or a hidden platform submerged below the surface of the water in a large tank of water (MWM) (Vorhees and Williams, 2014). The <span style="color:#3498db">Hebb-Williams maze measures an animal’s problem solving abilities by providing no spatial cues to find the target (Pritchett & Mulder, 2004).</span></p>
<p>2) Novel Object recognition. This is a simpler task that can be used to probe recognition memory. Two objects are presented to animal in an open field on trial 1, and these are explored. On trial 2, one object is replaced with a novel object and time spent interacting with the novel object is taken evidence of memory retention – I have seen one of these objects before, but not this one (Cohen and Stackman, 2015).</p>
<p>3) Contextual Fear conditioning is a hippocampal based learning task in which animals are placed in a novel environment and allowed to explore for several minutes before delivery of an aversive stimulus, typically a mild foot shock. Upon reintroduction to this same environment in the future (typically 24-48 hours after original training), animals will limit their exploration, the context of this chamber being associated with an aversive event. The degree of suppression of activity after training is taken as evidence of retention, i.e., memory (Curzon et al., 2009).</p>
<p>4) Trace fear conditioning. Standard fear conditioning paradigms require animals to make an association between a neutral conditioning stimulus (CS, a light or a tone) and an aversive stimulus (US, a footshock). The unconditioned response (CR) that is elicited upon delivery of the footshock US is freezing behavior. With repetition of CS/US delivery, the previously neutral stimulus comes to elicit the freezing response. This type of learning is dependent on the amygdala, a brain region associated with, but distinct from the hippocampus. Introducing a brief delay between presentation of the neutral CS and the aversive US, a trace period, requires the engagement of the amygdala and the hippocampus (Shors et al., 2001).</p>
<p><span style="color:#3498db">5) Operant Responding. Performance on operant responding reflects the cortex’ ability to organize processes (Rabin et al., 2002). </span></p>
<p><strong>In humans:</strong> A variety of standardized learning and memory tests have been developed for human neuropsychological testing, including children (Rohlman et al., 2008). These include episodic autobiographical memory, perceptual motor tests, short and long term memory tests, working memory tasks, word pair recognition memory; object location recognition memory. Some have been incorporated in general tests of intelligence (IQ) such as the Wechsler Adult Intelligence Scale (WAIS) and the Wechsler. Modifications have been made and norms developed for incorporating of tests of learning and memory in children. Examples of some of these tests include:</p>
<p>1) Rey Osterieth Complex Figure test (RCFT) which probes a variety of functions including as visuospatial abilities, memory, attention, planning, and working memory (Shin et al., 2006).</p>
<p>2) Children’s Auditory Verbal Learning Test (CAVLT) is a free recall of presented word lists that yields measures of Immediate Memory Span, Level of Learning, Immediate Recall, Delayed Recall, Recognition Accuracy, and Total Intrusions. (Lezak 1994; Talley, 1986).</p>
<p>3) Continuous Visual Memory Test (CVMT) measures visual learning and memory. It is a free recall of presented pictures/objects rather than words but that yields similar measures of Immediate Memory Span, Level of Learning, Immediate Recall, Delayed Recall, Recognition Accuracy, and Total Intrusions. (Lezak, 1984; 1994).</p>
<p>4) Story Recall from Wechsler Memory Scale (WMS) Logical Memory Test Battery, a standardized neurospychological test designed to measure memory functions (Lezak, 1994; Talley, 1986).</p>
<p>5) Autobiographical memory (AM) is the recollection of specific personal events in a multifaceted higher order cognitive process. It includes episodic memory- remembering of past events specific in time and place, in contrast to semantic autobiographical memory is the recollection of personal facts, traits, and general knowledge. Episodic AM is associated with greater activation of the hippocampus and a later and more gradual developmental trajectory. Absence of episodic memory in early life (infantile amnesia) is thought to reflect immature hippocampal function (Herold et al., 2015; Fivush, 2011).</p>
<p>6) Staged Autobiographical Memory Task. In this version of the AM test, children participate in a staged event involving a tour of the hospital, perform a series of tasks (counting footprints in the hall, identifying objects in wall display, buy lunch, watched a video). It is designed to contain unique event happenings, place, time, visual/sensory/perceptual details. Four to five months later, interviews are conducted using Children’s Autobiographical Interview and scored according to standardized scheme (Willoughby et al., 2014).</p>
<p><span style="color:#3498db">7) Attentional set-shifting (ATSET) task. Measures the ability to relearn cues over various schedules of reinforcement (Heisler et al., 2015).</span></p>
<p>8. Comprehensive developmental inventory for infants and toddlers (CDIIT). The CDIIT was designed and standardized in 1996, and it measures the global, cognitive, language, motor, gross motor, fine motor, social, self-help and behavioral developmental status of children from 3 to 71 months old (Wang et al., 1998).</p>
<p><strong>In Honey Bees:</strong> For over 50 years an assay for evaluating olfactory conditioning of the proboscis extension reflex (PER) has been used as a reliable method for evaluating appetitive learning and memory in honey bees (Guirfa and Sandoz, 2012; LaLone et al., 2017). These experiments pair a conditioned stimulus (e.g., an odor) with an unconditioned stimulus (e.g., sucrose) provided immediately afterward, which elicits the proboscis extension (Menzel, 2012). After conditioning, the odor alone will lead to the conditioned PER. This methodology has aided in the elucidation of five types of olfactory memory phases in honey bee, which include early short-term memory, late short-term memory, mid-term memory, early long-term memory, and late long-term memory (Guirfa and Sandoz, 2012). These phases are dependent on the type of conditioned stimulus, the intensity of the unconditioned stimulus, the number of conditioning trials, and the time between trials. Where formation of short-term memory occurs minutes after conditioning and decays within minutes, memory consolidation or stabilization of a memory trace after initial acquisition leads to mid-term memory, which lasts 1 d and is characterized by activity of the cAMP-dependent PKA (Guirfa and Sandoz, 2012). Multiple conditioning trials increase the duration of the memory after learning and coincide with increased Ca2+-calmodulin-dependent PKC activity (Guirfa and Sandoz, 2012). Early long-term memory, where a conditioned response can be evoked days to weeks after conditioning requires translation of existing mRNA, whereas late long-term memory requires de novo gene transcription and can last for weeks (Guirfa andSandoz, 2012)."</p>
<p>Basic forms of learning behavior such as habituation have been found in many taxa from worms to humans (Alexander, 1990). More complex cognitive processes such as executive function likely reside only in higher mammalian species such as non-human primates and humans. Recently, larval zebrafish has also been suggested as a model for the study of learning and memory (Roberts et al., 2013).</p>
<p><span style="color:#3498db"><strong>Life stage applicability: </strong>This key event is applicable to various life stages such as during brain development and maturity (Hladik & Tapio, 2016). </span></p>
<p><span style="color:#3498db"><strong>Sex applicability:</strong> This key event is not sex specific (Cekanaviciute et al., 2018), although sex-dependent cognitive outcomes have been recently ; Parihar et al., 2020). </span></p>
<p><span style="color:#3498db"><strong>Evidence for perturbation by a prototypic stressor: </strong>Current literature provides ample evidence of impaired learning and memory being induced by ionizing radiation (Cekanaviciute et al., 2018; Hladik & Tapio, 2016). </span></p>
HighMixedHighDuring brain developmentHighAdult, reproductively matureHighHighHighHighHighHigh<p>Aggleton JP, Brown MW. (1999) Episodic memory, amnesia, and the hippocampal-anterior thalamic axis. Behav Brain Sci. 22: 425-489.</p>
<p>Alexander RD (1990) Epigenetic rules and Darwinian algorithms: The adaptive study of learning and development. Ethology and Sociobiology 11:241-303.</p>
<p>Bellinger DC (2012) A strategy for comparing the contributions of environmental chemicals and other risk factors to neurodevelopment of children. Environ Health Perspect 120:501-507.</p>
<p>Burgess N (2002) The hippocampus, space, and viewpoints in episodic memory. Q J Exp Psychol A 55:1057-1080. Cohen, SJ and Stackman, RW. (2015). Assessing rodent hippocampal involvement in the novel object recognition task. A review. Behav. Brain Res. 285: 105-1176.</p>
<p><span style="color:#3498db">Cekanaviciute, E., S. Rosi and S. Costes. (2018), "Central Nervous System Responses to Simulated Galactic Cosmic Rays", International Journal of Molecular Sciences, Vol. 19/11, Multidisciplinary Digital Publishing Institute (MDPI) AG, Basel, https://doi.org/10.3390/ijms19113669. </span></p>
<p>Cohen, SJ and Stackman, RW. (2015). Assessing rodent hippocampal involvement in the novel object recognition task. A review. Behav. Brain Res. 285: 105-1176.</p>
<p>Curzon P, Rustay NR, Browman KE. Cued and Contextual Fear Conditioning for Rodents. In: Buccafusco JJ, editor. Methods of Behavior Analysis in Neuroscience. 2nd edition. Boca Raton (FL): CRC Press/Taylor & Francis; 2009.</p>
<p>D'Hooge R, De Deyn PP (2001) Applications of the Morris water maze in the study of learning and memory. Brain Res Brain Res Rev 36:60-90.</p>
<p>Doya K. (2000) Complementary roles of basal ganglia and cerebellum in learning and motor control. Curr Opin Neurobiol. 10: 732-739.</p>
<p>Eichenbaum H (2000) A cortical-hippocampal system for declarative memory. Nat Rev Neurosci 1:41-50.</p>
<p>Fivush R. The development of autobiographical memory. Annu Rev Psychol. 2011;62:559-82.</p>
<p>Gilbert ME, Sanchez-Huerta K, Wood C (2016) Mild Thyroid Hormone Insufficiency During Development Compromises Activity-Dependent Neuroplasticity in the Hippocampus of Adult Male Rats. Endocrinology 157:774-787.</p>
<p>Gilbert ME, Rovet J, Chen Z, Koibuchi N. (2012) Developmental thyroid hormone disruption: prevalence, environmental contaminants and neurodevelopmental consequences. Neurotoxicology 33: 842-52.</p>
<p>Gilbert ME, Sui L (2006) Dose-dependent reductions in spatial learning and synaptic function in the dentate gyrus of adult rats following developmental thyroid hormone insufficiency. Brain Res 1069:10-22.</p>
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54–66.</p>
<p>Herold, C, Lässer, MM, Schmid, LA, Seidl, U, Kong, L, Fellhauer, I, Thomann,PA, Essig, M and Schröder, J. (2015). Neuropsychology, Autobiographical Memory, and Hippocampal Volume in “Younger” and “Older” Patients with Chronic Schizophrenia. Front. Psychiatry, 6: 53.</p>
<p><span style="color:#3498db">Hladik, D. and S. Tapio. (2016), "Effects of ionizing radiation on the mammalian brain", Mutation Research/Reviews in Mutation Research, Vol. 770, Elsevier B. b., Amsterdam, https://doi.org/10.1016/j.mrrev.2016.08.003. </span></p>
<p><span style="color:#3498db">Heisler, J. M. et al. (2015), "The Attentional Set Shifting Task: A Measure of Cognitive Flexibility in Mice", Journal of Visualized Experiments, 96, JoVe, Cambridge, https://doi.org/10.3791/51944. Heisler, J. M. et al. (2015), "The Attentional Set Shifting Task: A Measure of Cognitive Flexibility in Mice", Journal of Visualized Experiments, 96, JoVe, Cambridge, https://doi.org/10.3791/51944. </span></p>
<p>LaLone, C.A., Villeneuve, D.L., Wu-Smart, J., Milsk, R.Y., Sappington, K., Garber, K.V., Housenger, J. and Ankley, G.T., 2017. Weight of evidence evaluation of a network of adverse outcome pathways linking activation of the nicotinic acetylcholine receptor in honey bees to colony death.<em> </em>STOTEN. 584-585, 751-775.</p>
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<p>Menzel, R., 2012. The honeybee as a model for understanding the basis of cognition. Nat. Rev. Neurosci. 13 (11), 758–768.</p>
<p>Mitchell AS, Dalrymple-Alford JC, Christie MA. (2002) Spatial working memory and the brainstem cholinergic innervation to the anterior thalamus. J Neurosci. 22: 1922-1928.</p>
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<p>OECD (2008) Nr 43 GUIDANCE DOCUMENT ON MAMMALIAN REPRODUCTIVE TOXICITY TESTING AND ASSESSMENT. ENV/JM/MONO(2008)16</p>
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<p> </p>
2016-11-29T18:41:242023-06-26T12:44:45Increased, Intracellular Calcium overloadIncreased, Intracellular Calcium overloadCellular<p>NMDAR agonist binding results in increased intracellular calcium, whereas NMDAR antagonist binding results in decreased intracellular calcium levels. For the relevant paragraphs below please see AOP entitled <em>Chronic binding of antagonist to N-methyl-D-aspartate receptors (NMDARs) during brain development induces impairment of learning and memory abilities.</em></p>
<p><strong>Biological state:</strong> KE <a href="/wiki/index.php/Event:52" title="Event:52"> Calcium influx, Decreased</a></p>
<p><strong>Biological compartments:</strong> KE <a href="/wiki/index.php/Event:52" title="Event:52"> Calcium influx, Decreased</a></p>
<p><strong>General role in biology:</strong> KE <a href="/wiki/index.php/Event:52" title="Event:52"> Calcium influx, Decreased</a></p>
<p><br />
The text specific for the AOP "ionotropic glutamatergic receptors and cognition” and “Acetylcholinesterase inhibition leading to neurodegeneration”:</p>
<p>It is now well accepted that modest activation of NMDARs leading to modest increases in postsynaptic calcium are optimal for triggering LTD (Lledo et al. 1998; Bloodgood and Sabatin, 2007; Bloodgood et al. 2009), whereas much stronger activation of NMDARs leading to much larger increases in postsynaptic calcium are required to trigger LTP (Luscher and Malenka, 2012; Malenka 1994). Indeed, high-frequency stimulation causes a strong temporal summation of the excitatory postsynaptic potentials (EPSPs), and depolarization of the postsynaptic cell is sufficient to relieve the Mg2+ block of the NMDAR and allow a large amount of calcium to enter into the postsynaptic cells. Therefore, intra-cellular calcium is measured as a readout for evaluation NMDAR stimulation.</p>
<p><em>Methods that have been previously reviewed and approved by a recognized authority should be included in the Overview section above. All other methods, including those well established in the published literature, should be described here. Consider the following criteria when describing each method: 1. Is the assay fit for purpose? 2. Is the assay directly or indirectly (i.e. a surrogate) related to a key event relevant to the final adverse effect in question? 3. Is the assay repeatable? 4. Is the assay reproducible? </em></p>
<p>Please see KE <a href="/wiki/index.php/Event:52" title="Event:52"> Calcium influx, Decreasedin</a> the AOP entitled: <em>Chronic binding of antagonist to N-methyl-D-aspartate receptors (NMDARs) during brain development induces impairment of learning and memory abilities.</em></p>
<p>Please see KE <a href="/wiki/index.php/Event:52" title="Event:52"> Calcium influx, Decreasedin</a> the AOP entitled <em>Chronic binding of antagonist to N-methyl-D-aspartate receptors (NMDARs) during brain development induces impairment of learning and memory abilities.</em></p>
<p> </p>
<p>Additional text, specific for the AOP “Acetylcholinesterase Inhibition leading to Neurodegeneration”:</p>
<p>Zebrafish have shown dysregulation in intracellular calcium ion levels following exposure to organophosphate compounds through similar mechanisms demonstrated in mammals <!--[if supportFields]><span
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style='mso-spacerun:yes'> </span>ADDIN EN.CITE
<EndNote><Cite><Author>Faria</Author><Year>2015</Year><RecNum>288</RecNum><DisplayText>(Faria
et al.
2015)</DisplayText><record><rec-number>288</rec-number><foreign-keys><key
app="EN" db-id="92990sdd8px5aie0tw7559riap0ffvxf0x5a"
timestamp="1569977726">288</key></foreign-keys><ref-type
name="Journal Article">17</ref-type><contributors><authors><author>Faria,
M.</author><author>Garcia-Reyero,
N.</author><author>Padrós, F.</author><author>Babin, P.
J.</author><author>Sebastián,
D.</author><author>Cachot, J.</author><author>Prats,
E.</author><author>Arick Ii, M.</author><author>Rial,
E.</author><author>Knoll-Gellida,
A.</author><author>Mathieu, G.</author><author>Le
Bihanic, F.</author><author>Escalon, B.
L.</author><author>Zorzano, A.</author><author>Soares,
A. M.</author><author>Raldúa,
D.</author></authors></contributors><titles><title>Zebrafish
Models for Human Acute Organophosphorus
Poisoning</title><secondary-title>Sci
Rep</secondary-title></titles><periodical><full-title>Sci
Rep</full-title></periodical><pages>15591</pages><volume>5</volume><edition>2015/10/22</edition><keywords><keyword>Acetylcholinesterase</keyword><keyword>Animals</keyword><keyword>Chemical
Terrorism</keyword><keyword>Chlorpyrifos</keyword><keyword>Disease
Models, Animal</keyword><keyword>Humans</keyword><keyword>Organophosphate
Poisoning</keyword><keyword>Small Molecule
Libraries</keyword><keyword>Zebrafish</keyword></keywords><dates><year>2015</year><pub-dates><date>Oct</date></pub-dates></dates><isbn>2045-2322</isbn><accession-num>26489395</accession-num><urls><related-urls><url>https://www.ncbi.nlm.nih.gov/pubmed/26489395</url><url>https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4614985/pdf/srep15591.pdf</url></related-urls></urls><custom2>PMC4614985</custom2><electronic-resource-num>10.1038/srep15591</electronic-resource-num><language>eng</language></record></Cite></EndNote><span
style='mso-element:field-separator'></span></span><![endif]-->(Faria et al. 2015)<!--[if supportFields]><span style='font-size:11.0pt;
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text1'><span style='mso-element:field-end'></span></span><![endif]-->.</p>
CL:0000255eukaryotic cellHigh<p>Bloodgood BL, Sabatini BL., Nonlinear regulation of unitary synaptic signals by CaV2.3 voltage-sensitive calcium channels located in dendritic spines. Neuron, 2007, 53:249–260.</p>
<p>Bloodgood BL, Giessel AJ, Sabatini BL., Biphasic synaptic Ca influx arising from compartmentalized electrical signals in dendritic spines. PLoS Biol., 2009, 7: e1000190.</p>
<p>Faria, M., N. Garcia-Reyero, F. Padrós, P. J. Babin, D. Sebastián, J. Cachot, E. Prats, M. Arick Ii, E. Rial, A. Knoll-Gellida, G. Mathieu, F. Le Bihanic, B. L. Escalon, A. Zorzano, A. M. Soares and D. Raldúa (2015), "Zebrafish Models for Human Acute Organophosphorus Poisoning.” <em>Sci Rep</em> <strong>5</strong>. DOI: 10.1038/srep15591.</p>
<p>Lledo PM, Zhang X, Sudhof TC, Malenka RC, Nicoll RA., Postsynaptic membrane fusion and long-term potentiation. Science, 1998, 279: 399–403.</p>
<p>Malenka RC. Synaptic plasticity in the hippocampus: LTP and LTD. Cell, 1994, 78: 535–538.</p>
<p>Luscher C. and Robert C. Malenka. NMDA Receptor-Dependent Long-Term Potentiation and Long-Term Depression (LTP/LTD). Cold Spring Harb Perspect Biol., 2012, 4: a005710.</p>
2016-11-29T18:41:242020-06-26T04:45:09Decrease of neuronal network functionNeuronal network function, DecreasedOrgan<p><strong>Biological state:</strong> There are striking differences in neuronal network formation and function among the developing and mature brain. The developing brain shows a slow maturation and a transient passage from spontaneous, long-duration action potentials to synaptically-triggered, short-duration action potentials.</p>
<p>Furthermore, at this precise developmental stage the neuronal network is characterised by "hyperexcitability”, which is related to the increased number of local circuit recurrent excitatory synapses and the lack of γ-amino-butyric acid A (GABAA)-mediated inhibitory function that appears much later. This “hyperexcitability” disappears with maturation when pairing of the pre- and postsynaptic partners occurs and synapses are formed generating population of postsynaptic potentials and population of spikes followed by developmental GABA switch. Glutamatergic neurotransmission is dominant at early stages of development and NMDA receptor-mediated synaptic currents are far more times longer than those in maturation, allowing more calcium to enter the neurons. The processes that are involved in increased calcium influx and the subsequent intracellular events seem to play a critical role in establishment of wiring of neural circuits and strengthening of synaptic connections during development (reviewed in Erecinska et al., 2004). Neurons that do not receive glutaminergic stimulation are undergoing developmental apoptosis.</p>
<p>During the neonatal period, the brain is subject to profound alterations in neuronal circuitry due to high levels of synaptogenesis and gliogenesis. For example, in neuroendocrine regions such as the preoptic area-anterior hypothalamus (POA-AH), the site of gonadotropin-releasing hormone (GnRH) system is developmentally regulated by glutamatergic neurons. The changes in the expression of the N-methyl-D-aspartate (NMDA) receptor subunits NR1 and NR2B system begin early in postnatal development, before the onset of puberty, thereby playing a role in establishing the appropriate environment for the subsequent maturation of GnRH neurons (Adams et al., 1999).</p>
<p><strong>Biological compartments:</strong> Neural network formation and function happen in all brain regions but it appears to onset at different time points of development (reviewed in Erecinska et al., 2004). Glutamatergic neurotransmission in hippocampus is poorly developed at birth. Initially, NMDA receptors play important role but the vast majority of these premature glutamatergic synapses are “silent” possibly due to delayed development of hippocampal AMPA receptors. In contrast, in the cerebral cortex the maturation of excitatory glutamatergic neurotransmission happens much earlier. The “silent” synapses disappear by PND 7-8 in both brain regions mentioned above.</p>
<p>There is strong evidence suggesting that NMDA receptor subunit composition controls synaptogenesis and synapse stabilization (Gambrill and Barria, 2011). It is established fact that during early postnatal development in the rat hippocampus, synaptogenesis occurs in parallel with a developmental switch in the subunit composition of NMDA receptors from NR2B to NR2A. It is suggested that early expression of NR2A in organotypic hippocampal slices reduces the number of synapses and the volume and dynamics of spines. In contrast, overexpression of NR2B does not affect the normal number and growth of synapses. However, it does increase spine motility, adding and retracting spines at a higher rate. The C terminus of NR2B, and specifically its ability to bind CaMKII, is sufficient to allow proper synapse formation and maturation. Conversely, the C terminus of NR2A was sufficient to stop the development of synapse number and spine growth. These results indicate that the ratio of synaptic NR2B over NR2A controls spine motility and synaptogenesis, and suggest a structural role for the intracellular C terminus of NR2 in recruiting the signalling and scaffolding molecules necessary for proper synaptogenesis. Interestingly, it was found that genetic deletion of NR3A accelerates glutamatergic synaptic transmission, as measured by AMPAR-mediated postsynaptic currents recorded in hippocampal CA1. Consistent, the deletion of NR3A accelerates the expression of the glutamate receptor subunits NR1, NR2A, and GluR1 sugesting that glutamatergic synapse maturation is critically dependent upon activation of NMDA-type glutamate receptors (Henson et al., 2012).</p>
<p><strong>General role in biology:</strong> The development of neuronal networks can be distinguished into two phases: an early ‘establishment’ phase of neuronal connections, where activity-dependent and independent mechanisms could operate, and a later ‘maintenance’ phase, which appears to be controlled by neuronal activity (Yuste and Sur, 1999). These neuronal networks facilitate information flow that is necessary to produce complex behaviors, including learning and memory (Mayford et al., 2012).</p>
<p><em>Methods that have been previously reviewed and approved by a recognized authority should be included in the Overview section above. All other methods, including those well established in the published literature, should be described here. Consider the following criteria when describing each method: 1. Is the assay fit for purpose? 2. Is the assay directly or indirectly (i.e. a surrogate) related to a key event relevant to the final adverse effect in question? 3. Is the assay repeatable? 4. Is the assay reproducible? </em></p>
<p><strong>In vivo:</strong> The recording of brain activity by using electroencephalography (EEG), electrocorticography (ECoG) and local field potentials (LFP) assists towards the collection of signals generated by multiple neuronal cell networks. Advances in computer technology have allowed quantification of the EEG and expansion of quantitative EEG (qEEG) analysis providing a sensitive tool for time-course studies of different compounds acting on neuronal networks' function (Binienda et al., 2011). The number of excitatory or inhibitory synapses can be functionally studied at an electrophysiological level by examining the contribution of glutamatergic and GABAergic synaptic inputs. The number of them can be determined by variably clamping the membrane potential and recording excitatory and inhibitory postsynaptic currents (EPSCs or IPSCs) (Liu, 2004).</p>
<p><strong>In vitro:</strong> Microelectrode array (MEA) recordings are also used to measure electrical activity in cultured neurons (Keefer et al., 2001, Gramowski et al., 2000; Gopal, 2003; Johnstone et al., 2010). MEAs can be applied in high throughput platforms to facilitate screening of numerous chemical compounds (McConnell et al., 2012). Using selective agonists and antagonists of different classes of receptors their response can be evaluated in a quantitative manner (Novellino et al., 2011; Hogberg et al., 2011).</p>
<p>Patch clamping technique can also be used to measure neuronal network activity.In some cases, if required, planar patch clamping technique can also be used to measure neuronal networks activity (e.g., Bosca et al., 2014).</p>
<p>In vitro studies in brain slices applying electrophysiological techniques showed significant variability among species (immature rats, rabbits and kittens) related to synaptic latency, duration, amplitude and efficacy in spike initiation (reviewed in Erecinska et al., 2004).</p>
UBERON:0000955brainHighMixedHighDuring brain developmentHighHighHighHigh<p>Adams MM, Flagg RA, Gore AC., Perinatal changes in hypothalamic N-methyl-D-aspartate receptors and their relationship to gonadotropin-releasing hormone neurons. Endocrinology. 1999 May;140(5):2288-96.</p>
<p>Binienda ZK, Beaudoin MA, Thorn BT, Ali SF. (2011) Analysis of electrical brain waves in neurotoxicology: γ-hydroxybutyrate. Curr Neuropharmacol. 9: 236-239.</p>
<p>Bosca, A., M. Martina, and C. Py (2014) Planar patch clamp for neuronal networks--considerations and future perspectives. Methods Mol Biol, 2014. 1183: p. 93-113.</p>
<p>Erecinska M, Cherian S, Silver IA. (2004) Energy metabolism in mammalian brain during development. Prog Neurobiol. 73: 397-445.</p>
<p>Gambrill AC, Barria A. NMDA receptor subunit composition controls synaptogenesis and synapse stabilization. Proc Natl Acad Sci U S A. 2011:108(14):5855-60.</p>
<p>Gopal K. (2003) Neurotoxic effects of mercury on auditory cortex networks growing on microelectrode arrays: a preliminary analysis. Neurotoxicol Teratol. 25: 69-76.</p>
<p>Gramowski A, Schiffmann D, Gross GW. (2000) Quantification of acute neurotoxic effects of trimethyltin using neuronal networks cultures on microelectrode arrays. Neurotoxicology 21: 331-342.</p>
<p>Henson MA, Larsen RS, Lawson SN, Pérez-Otaño I, Nakanishi N, Lipton SA, Philpot BD. (2012) Genetic deletion of NR3A accelerates glutamatergic synapse maturation. PLoS One. 7(8).</p>
<p>Hogberg HT, Sobanski T, Novellino A, Whelan M, Weiss DG, Bal-Price AK. (2011) Application of micro-electrode arrays (MEAs) as an emerging technology for developmental neurotoxicity: evaluation of domoic acid-induced effects in primary cultures of rat cortical neurons. Neurotoxicology 32: 158-168.</p>
<p>Johnstone AFM, Gross GW, Weiss D, Schroeder O, Shafer TJ. (2010) Use of microelectrode arrays for neurotoxicity testing in the 21st century Neurotoxicology 31: 331-350.</p>
<p>Keefer E, Norton S, Boyle N, Talesa V, Gross G. (2001) Acute toxicity screening of novel AChE inhibitors using neuronal networks on microelectrode arrays. Neurotoxicology 22: 3-12.</p>
<p>Liu G. (2004) Local structural balance and functional interaction of excitatory and inhibitory synapses in hippocampal dendrites. Nat Neurosci. 7: 373-379.</p>
<p>Mayford M, Siegelbaum SA, Kandel ER. (2012) Synapses and memory storage. Cold Spring Harb Perspect Biol. 4. pii: a005751.</p>
<p>McConnell ER, McClain MA, Ross J, LeFew WR, Shafer TJ. (2012) Evaluation of multi-well microelectrode arrays for neurotoxicity screening using a chemical training set. Neurotoxicology 33: 1048-1057.</p>
<p>Novellino A, Scelfo B, Palosaari T, Price A, Sobanski T, Shafer TJ, Johnstone AF, Gross GW, Gramowski A, Schroeder O, Jügelt K, Chiappalone M, Benfenati F, Martinoia S, Tedesco MT, Defranchi E, D'Angelo P, Whelan M. (2011) Development of micro-electrode array based tests for neurotoxicity: assessment of interlaboratory reproducibility with neuroactive chemicals. Front Neuroeng. 4: 4.</p>
<p>Yuste R, Peinado A, Katz LC. (1992) Neuronal domains in developing neocortex. Science 257: 665-669.</p>
2016-11-29T18:41:242018-05-28T11:36:00da37a0f1-77f9-4644-9093-ca2938f64d567d9f8e68-0007-4ef4-bcf7-1f4a7aeefcc1<p>NMDARs can be activated indirectly through initial activation of KA/AMPARs as it happens in the case of DomA exposure. DomA is an agonist of
presynaptic and postsynaptic KARs and sustained activation of these receptors by DomA results in massive ion flux and excessive release of glutamate
from excitatory terminals causing depolarization of the postsynaptic neuron (as descibed in MIE). Upon this depolarization the Mg2+ block is removed
from the pore of NMDARs, resulting in their activation allowing sodium, potassium, and, importantly, calcium ions to enter into a cell. The sustained
exposure to DomA causes pathological overactivation of NMDARs.
In the case of exposure to glufosinate NMDARs activation is triggered by direct, sustained binding of glufosinate to the NMDARs.
</p><p>NMDARs are unique among ligand-gated ion channels in that their activation requires binding of two co-agonists, glycine and endogenous
neurotransmitter, L-glutamate. Physiologically, however, glycine and glutamate have distinct functions. While L-glutamate is released from specific
presynaptic terminals, low concentrations of ambient glycine present at the synapse are thought to be sufficient to allow receptor activation.
There is a clear understanding that binding of glutamate or its analogue will activate NMDA receptor (accepted dogma). The prolonged activation of
NMDARs will lead to a pathological over-activation of a receptor leading to excitotoxicity (minor role of KA/AMPARs), allowing high levels of calcium
ions to enter the cell. However, KA/AMPARs play an important role for indirect NMDAR activation since (almost always) an initial activation of these
receptors triggers depolarization of postsynaptic neurons that relieves the block of the channel pore by Mg2+, resulting in NMDAR activation.
NMDA receptors are formed by a ligand binding domain (LBD) and an ion channel that are considered the core structural and functional elements of
the receptors. There is a clear understanding of how agonist binding leads to channel opening that relies on structural (e.g. crystallography or NMR)
and functional (e.g. UV and IR spectrometric measurements) experimental studies of the water-soluble LBD combined with functional studies of the
intact receptor. After the initial agonist binding, a conformational change—so-called clam shell closure—that prevents agonist dissociation occurs
followed by a conformational change in the ion channel that is tightly coupled to that in the LBD (reviewed in Traynelis et al., 2010).
Consequently it can be stated that there is a clear structural and functional mechanistic understanding in this KER between MIE (Binding of agonist to
glutamate ionotropic receptors) and KE1, NMDAR overactivation that, as explained above, can be triggered by direct binding to NMDAR or indirectly,
through initial activation of KA/AMPARs as it happens in the case of exposure to glufosinate and DomA respectively, two stressors described in this
AOP.
</p><p>Indeed, domoic acid has a very strong affinity for the ionotropic glutamate receptors, the activation of which results in excitotoxicity, initiated by an
integrative action of ionotropic receptors at both sides of the synapse blocking the channel from rapid desensitization. It has a synergistic effect with
endogenous glutamate and it acts mainly as an agonist for presynaptic and postsynaptic kainate receptors. Activation of ionotropic receptors leads to
the influx of Na+, K+ and Ca2+, particulary after activation of NMDARs. In combination with the inhibitory GABA neurotransmitter, glutamate
contributes to the control of overall neuronal excitability.
</p><p>Gufosinate (GLF) triggers alterations in glutamatergic signaling through direct binding and activation of NMDARs (Lantz et al., 2014: Matsumura et al.,
2001). GLF agonist action at the NMDAR is expected to occur through interaction with the glutamate binding site and requires binding of the glycine
co-agonist as well as release of the magnesium block from the channel pore. Additionally, the possible inhibition by GLF of the high affinity glutamate
re-uptake transporter, especially GLT-I was studied to determine whether GLF could increase the levels of endogenous glutamate at the synaptic cleft,
resulting in over activation of NMDARs. Such mechanism was excluded by Lantz (Lantz et al., 2014) but suggested by other studies (Watanabe and
Sano, 1998).
</p><p><em>
Include consideration of temporal concordance here
</em>
</p><p>There is well established understanding of NMDAR activation by endogenous agonist glutamate that happens in the absence of the Mg2+ block under
conditions of depolarized post-synaptic membrane(accepted dogma) (Blanke et al., 2009a and b; Enoki R, et al.,2004).
</p><p>Single channel behavior of NMDARs from hippocampal CA1 neurons was studied using very low glutamate concentrations to improve temporal
resolution of individual glutamate binding events. Openings resulting from individual receptor activations showed surprising complexity: they consist of
a long cluster of bursts of openings. Furthermore, the NMDARs appeared to have different gating modes, occasionally entering periods of very high
open probability (Gibb et al., 1991).
Single channel analysis also provided insight in how NMDARs function at the synapse. In response to a brief pulse of glutamate, mimicking synaptic
release, NMDARs activate slowly over hundreds of milliseconds and continue activating long after all glutamate has been removed from the synaptic
cleft, thereby briefly “memorizing” the occurrence of a synaptic input. Single channel analysis of NR1 and NR2A receptors indicates that after a brief
pulse of glutamate, receptors enter a high affinity closed state from which either channel opening or agonist unbinding occurs with approximately
equal probability (Popescu et al., 2004). A single synaptic event is therefore expected to only partially activate NMDARs. Consequently, a closely
spaced second pulse of agonist is able to further increase the open probability, endowing the NMDAR with an ability to decode synaptic input
frequency.
</p><p><b>Domoic acid</b> is an agonist for presynaptic and postsynaptic kainate receptors, however indirectly also activates NMDA receptors. Kainate receptors
are localized both at presynaptic and postsynaptic sites. At presynaptic sites, they directly affect transmitter release from both excitatory and inhibitory
neuron terminals. At postsynaptic sites, kainate receptors lead to cell depolarization, which would bring the neuron closer to its spike firing threshold.
By having this dual localization, kainate receptors help in the control of neuronal excitability. However, sustained activation of postsynaptic kainate
receptors by domoic acid results in massive ion flux and excessive release of glutamate from excitatory terminals. The released glutamate in turn
activates NMDA receptors, which have lost their physiologic Mg2++ block because of domoic acid–induced depolarization. The final event is an
increase of NMDA-mediated Ca2++ flux and subsequent activation of intracellular pro-oxidative cascades and ion imbalances, eventually leading to
excitotoxicity-mediated neuronal death (Babot et al., 2005;Giordano et al., 2006).
</p><p>Kainate receptors are widely expressed in the hippocampus. Glutamatergic granule cells in the hippocampus express these receptors, suggesting that
cell death found after domoic acid intoxication may be produced by hyperstimulation of NMDA receptor after glutamate is released in excess. In
agreement with this hypothesis, the seriously damaged CA3 area of the hippocampus receives projections from hippocampal granule cells. Qiu and
Curras-Collazo (Qiu et al., 2006a) elegantly demonstrated that domoic acid first targets kainate receptors in the hippocampus by blocking its effects in
vivo with a kainate receptor antagonist. The sequential involvement of distinct glutamate receptors was confirmed and further elucidated in rat mixed
cortical cell and hippocampal slice cultures (Jakobsen et al., 2002; Qiu et al., 2006b).
</p><p>Using primary cultures of rodent cerebellar granule cells, an in vitro model mainly constituted by glutamatergic neurons that express both NMDA and
kainate receptors it was proved that domoic acid increased glutamate release, intracellular calcium, and cell death, which were prevented by kainate
and NMDA receptor antagonists (Berman and Murray, 1997; Vale-Gonzalez et al., 2006) confirming that DomA toxicity is mediated by both KA and
NMDARs.
</p><p><b>Glufosinate</b> (GLF) and its primary metabolite N-acetylglufosinate (NAcGLF) interaction with NMDARs was studied in the primary culture of rat cortical
neurons by performing [3H]CGP 39653 binding experiments. The results showed that their binding affinity to NMDAR (IC50, GLF 668 uM and NAcGLF
approximately 100 uM) corresponded to the concentration that produce the highest increase of mean firing rate. Furthermore, they produced biphasic
MFR profile, specific to NMDAR agonists. The obtained results suggest that GLF and NAcGLF can produce both effects,excitatory and inhibitory on
network activity through direct activation of NMDARs (Lantz et al., 2014).
</p><p>Direct activation of NMDARs by GLF is also suggested by in vivo studies where three NMDA receptor antagonists, dizocilpine, LY235959, and Compound
40, and AMPA/KA antagonist, NBQX, were co-administrated with glufosinate ammonium (80 mg/kg, intraperitoneally) in mice. Statistical analyses
showed that the NMDA receptor antagonists markedly inhibited the GLF-induced convulsions, while the AMPA/KA receptor antagonist had no effect.
These results suggest that the convulsion caused by glufosinate ammonium were mediated through activation of NMDA receptors (Matsumura et al.,
2001).
</p><p>The increase in MFR induced by GLF in neuronal networks was significantly blocked by MK-801 but not entirely suggesting that GLF can increase
activity in the MEA system through non-synaptic NMDARs, since these are not blocked by MK-801.
It is not entirely clear whether GLF can work through an inhibition of the glutamate reuptake transporter, GLT-I, increasing the concentration of
endogenous glutamate at the synaptic cleft and subsequently resulting in over activation of NMDARs (Lantz et al., 2014: Watanabe and Sano, 1998).
Further studies are necessary to determine whether this alternative mechanism of GLF-induced NMDAR overactivation takes place.
Additionally GLF also modulates glutamine synthetase (GS) activity. Since, astrocytic GS in the brain participates in the metabolic regulation of glutamate (endogenous agonist of NMDAR) it is not clear if this pathway contributes to NMDAR activation too.
</p><p><em>
Is it known how much change in the first event is needed to impact the second?
Are there known modulators of the response-response relationships?
Are there models or extrapolation approaches that help describe those relationships?
</em>
</p><p>To predict how potent an agonist can be, it is usually based on the half maximal effective concentration (EC50) that induces the currents through
NMDA receptors of brain slices and cells (or in recombinantly expressed proteins of these receptors). Traynelis et al. 2010 summarised the IC50 values
for agonists of the different NMDA receptor subunits.
The activation effect (efficacy) of agonist on NMDA receptor have been found to be dependent on:
-the type of subunits that form the NMDA receptor
-the chemical structure of the agonist
-the binding site of a receptor that the agonist prefers
-how tightly an agonist binds to the receptor (affinity)
Glufosinate and its primary metabolite N-acetylglufosinate NAcGLF bind to the NMDAR with the following affinity: the IC50 value for GLF was 668 mM
and for NAcGLF was about 100 mM.
</p><p>Various studies suggest the existence of functional NMDA-like receptors in invertebrates (Xia et al., 2005). Fly and rodent NMDARs exhibit several
important differences (Murphy and Glanzman, 1997). The expression and function of NMDA receptors in rodent and primates is well characterized in
the existing literature.
</p><p><br />
Babot Z, Cristofol R, Sun˜ol C.,Excitotoxic death induced by released glutamate in depolarized primary cultures of mouse cerebellar granule cells is
dependent on GABAA receptors and niflumic acidsensitive chloride channels. Eur J Neurosci., 2005, 21: 103–112.
</p><p>Blanke ML, VanDongen AMJ., Activation Mechanisms of the NMDA Receptor. In: Van Dongen AM, editor. Biology of the NMDA Receptor. Boca Raton
(FL): CRC Press; 2009a. Chapter 13. Frontiers in Neuroscience.
</p><p>Blanke ML., and Antonius M.J. VanDongen, Activation Mechanisms of the NMDA Receptor in Biology of the NMDA Receptor,2009b, Chapter 13, Van Dongen AM, editor. Boca Raton (FL): CRC Press.
</p><p>Berman FW, Murray TF., Domoic acid neurotoxicity in cultured cerebellar granule neurons is mediated predominantly by NMDA receptors that are
activated as a consequence of excitatory amino acid release. J Neurochem., 1997, 69: 693–703.
</p><p>Enoki R, et al., NMDAR-mediated depolarizing after-potentials in the basal dendrites of CA1 pyramidal neurons. Neurosci Res., 2004, 48: 325-337.
</p><p>Gibb AJ, Colquhoun D. Glutamate activation of a single NMDAR-channel produces a cluster of channel openings. Proc. R. Soc. Lond. (Biol.) 1991, 243:
39-47.
</p><p>Giordano G, White CC, McConnachie LA, Fernandez C, Kavanagh TJ, Costa LG., Neurotoxicity of domoic Acid in cerebellar granule neurons in a genetic
model of glutathione deficiency. Mol Pharmacol., 2006, 70: 2116–2126.
</p><p>Jakobsen B, Tasker A, Zimmer J., Domoic acid neurotoxicity in hippocampal slice cultures. Amino Acids, 2002, 23: 37–44.
</p><p>Lantz Stephen R , Cina M. Mack , Kathleen Wallace, Ellen F. Key , Timothy J. Shafer , John E. Casida, Glufosinate binds to N-methyl-D-aspartate
receptors and increases neuronal network activity in vitro. NeuroToxicology, 2014, 45: 38–47.
</p><p>Matsumura N1, Takeuchi C, Hishikawa K, Fujii T, Nakaki T., Glufosinate ammonium induces convulsion through N-methyl-D-aspartate receptors in
mice. Neurosci Lett., 2001, 304(1-2): 123-5.
</p><p>Murphy GG, Glanzman DL., Mediation of classical conditioning in Aplysia californica by long-term potentiation of sensorimotor synapses. Science, 1997,
278: 467-78.
</p><p>Popescu G, et al. Reaction mechanism determines NMDAR response to repetitive stimulation. Nature. 2004, 430: 790-799.
</p><p>Qiu S, Curras-Collazo MC., Histopathological and molecular changes produced by hippocampal microinjection of domoic acid. Neurotoxicol Teratol.,
2006a, 28: 354–362.
</p><p>Qiu S, Pak CW, Curras-Collazo MC., Sequential involvement of distinct glutamate receptors in domoic acid-induced neurotoxicity in rat mixed cortical
cultures: Effect of multiple dose/duration paradigms, chronological age, and repeated exposure. Toxicol Sci., 2006b, 89: 243–256.
</p><p>Traynelis SF, Wollmuth LP, McBain CJ, Menniti FS, Vance KM, Ogden KK, Hansen KB, Yuan H, Myers SJ, Dingledine R., Glutamate receptor ion
channels: structure, regulation, and function. Pharmacol Rev., 2010, 62(3):405-96.
</p><p>Vale-Gonzalez C, Alfonso A, Sun˜ol C, Vieytes MR, Botana LM., Role of the plasma membrane calcium adenosine triphosphatase on domoate-induced
intracellular acidification in primary cultures of cerebellar granule cells. J Neurosci Res., 2006, 84: 326–337.
</p><p>Watanabe T1, Sano T., Neurological effects of glufosinate poisoning with a brief review. Hum Exp Toxicol. 1998, 17: 35-9.
</p><p>Xia S, et al., NMDARs mediate olfactory learning and memory in Drosophila. Curr Biol., 2005, 15:603-618.
</p>2016-11-29T18:41:352016-11-29T20:44:067d9f8e68-0007-4ef4-bcf7-1f4a7aeefcc112820d47-746d-49b4-8c7b-6ad40e68227f2022-12-11T21:08:072022-12-11T21:08:077d9f8e68-0007-4ef4-bcf7-1f4a7aeefcc1860a6895-936b-4295-8a97-a8a7ed2f68f9<p>The NMDA receptor is distinct from the other glutamate receptors in two ways: first, it is both ligand-gated and voltage-dependent; second, it requires co-activation by two ligands: glutamate and either glycine or D-serine. Following membrane depolarization, the co-agonists, L-glutamate and glycine must bind to their respective sites on the receptor to open the channel. On activation, the NMDA receptor allows the influx of extracellular calcium ions into the postsynaptic neuron and neurotransmission occurs (reviewed in Higley and Sabatini, 2012). Calcium flux through NMDA receptors is also thought to be critical in synaptic plasticity, a cellular mechanism for learning and memory. Indeed, NMDA receptor–dependent synaptic potentiation (LTP) and depression (LTD) are two forms of activity-dependent long-term changes in synaptic efficacy that are believed to represent cellular correlates of learning and memory processes. The best characterized form of NMDA receptor-dependent LTP and LTD occurs between CA3 and CA1 pyramidal neurons of the hippocampus (Luscher and Malenka, 2012). It is now well established that modest activation of NMDARs leads to modest increases in postsynaptic calcium, triggering LTD, whereas much stronger activation of NMDARs leading to much larger increases in postsynaptic calcium are required to trigger LTP (Luscher and Malenka, 2012). The high-frequency stimulation causes a strong temporal summation of the excitatory postsynaptic potentials, and depolarization of the postsynaptic cell is sufficient to relieve the Mg2+ block of the NMDAR and allow a large amount of calcium to enter into the post-synaptic cells.</p>
<p><span style="font-family:Arial,Helvetica,sans-serif"><span style="font-size:12pt"><span style="background-color:white"><span style="font-size:10.5pt">There is structural and functional mechanistic understanding supporting this relationship between NMDAR overactivation and increased intracellular calcium.</span></span></span></span></p>
<p>The relationship between the upstream and downstream key event is plausible as the expression of the functional NMDA receptors is commonly carried out or assessed by Ca2+ imaging method. Calcium imaging techniques have been extensively utilized in the literature to investigate the potential interactions between NMDA-evoked Ca2+ influx and NMDA receptor activation. Approximately 15% of the current through NMDA receptors is mediated by Ca2+ under physiological conditions (Higley and Sabatini, 2012).</p>
<p>It has been shown that less than five and, occasionally, only a single NMDA receptor opens under physiological conditions, causing a total Ca2+ influx of about 6000 ions into a spine head reaching a concentration of ∼10 µm (Higley and Sabatini, 2012). However, the majority of the ions are rapidly eliminated by binding to Ca2+ proteins, reaching ∼1 µM of free Ca2+ concentration (Higley and Sabatini, 2012).</p>
<p>It has been shown that in rat primary forebrain cultures the intracellular Ca2+ increases after activation of the NMDA receptor through administration of NMDA but this increase in Ca2+ is blocked when the cells are cultured under Ca2+ free conditions, demonstrating that the NMDA-evoked increase in intracellular Ca2+ derives from extracellular and not intracellular sources (Liu et al., 2013).</p>
<p>Indirect mechanism of domoic acid (DA) induced overactivation of NMDARs that result in Ca2+ overload: depolarization of the pre-synaptic cell activates the release of endogenous Ca2+ which mobilizes vesicles containing GLU to the membrane surface. Glutamate (GLU) is then released into the synaptic cleft by exocytosis where it is able to interact with cell surface receptors. Exogenous DA can interact within the synaptic cleft with each of the three ionotropic receptor subtypes including the kainate, AMPA, and NMDA receptors on cell membranes. Activation of the kainate and AMPA receptors results in release of Ca2+ via coupled ion channels, into the post-synaptic cell. DA is also able to bind to NMDA receptors that are linked to both Ca2+ and NA/K+ ion channels and results in a cellular influx of both Na+ and Ca2+. Unlike GLU, DA induces prolonged receptor activation causing a constant influx of cations into the cell and the appropriate chemical cues for desensitization are blocked. The excess intracellular Ca2+ causes disruption of cellular function, cell swelling and ultimately cell death (Lefebvre and Robertson,2010).</p>
<p>Glufosinate (GLF) is the methylphosphinate analog of glutamate that directly can activate NMDARs (Lantz et al., 2014, Matsumura et al., 2001, Faro et al., 2013) (as described in KE: <em>NMDARs, Binding of agonist</em>). It is well established in the existing literature that activation of NMDARs leads to the intra-cellular Ca2+ overload and based on this assumption it can be suggested that an exposure to GLF leads to increased intra-cellular calcium levels.</p>
<p><em>Include consideration of temporal concordance here </em></p>
<p><strong>Domoic acid (DomA)</strong></p>
<ul>
<li>Treatment of mouse cerebellar granule neurons (CGNs) with 1 or 10 µM DomA causes increase of intracellular Ca2+ by approximately 5 or 8 fold compared to controls, respectively (Giordano et al., 2006). Interestingly, when the cells are exposed simultaneously to DomA and the NMDA receptor antagonist MK-801, the Ca2+ levels measured are close to control levels, indicating that the Ca2+ elevation evoked by DomA involves activation of NMDA receptors (Giordano et al., 2006).</li>
</ul>
<ul>
<li>The same research group has performed a time course study by applying a high and a low DomA concentration and using CGNs from Gclm (+/+) and Gclm (−/−) mice lacking glutathione (Giordano et al., 2007). The low DomA dose (0.1μM) causes a small and delayed increase in intracellular Ca2+ concentration with a full recovery by 20 min. When the experiment is performed in the absence of extracellular calcium, this increase of intracellular Ca2+ levels in the presence of DomA is abolished, indicating that this change in homeostasis of Ca2+ is due to ion entry from outside the cell. However, this recording of intracellular Ca2+ is antagonised only by NBQX (AMPA receptor antagonist), but not by MK-801 (NMDA receptor antagonist). On the other hand, the higher DomA concentration (10μM) causes a rapid and robust increase in intracellular Ca2+, which lasts even after 25 min. This effect is antagonized by both NBQX and MK-801, suggesting that not only AMPA but also NMDA receptors are involved in Ca2+ elevation evoked by DomA at high doses (Giordano et al., 2007).</li>
</ul>
<ul>
<li>In an earlier study, the time course and concentration dependence of the increase in intracellular Ca2+ stimulated by DomA has been examined in 10-13 day-in-culture CGNs (Berman et al., 2002). DomA produces a rapid and concentration-dependent increase in intracellular Ca2+, showing the maximal increase at 10 μM DomA (Berman et al., 2002). At this concentration, fluo-3 fluorescence that is used to measure Ca2+ elevates rapidly during the first 40 s of exposure, increases more slowly before peaking at 3.5 min, after which the signal diminishes steadily over the 30 min course of the experiment to 55% of peak values. The EC50 for DomA-induced increase in intracellular Ca2+ is 0.61 μM. In the same study, the NMDA receptor antagonist MK-801 significantly reduced both peak and final plateau of intracellular Ca2+ by 30 and 70%, respectively (Berman et al., 2002).</li>
</ul>
<ul>
<li>These three studies (Giordano et al., 2006; 2007; Berman et al., 2002) do not provide a simultaneous measurement of NMDA receptor activation by DomA and intracellular Ca2+ levels. However, they do provide indirect evidence of NMDA receptor activation involvement in increased intracellular Ca2+ concentrations induced by DomA as they have used known antagonists of the NMDA receptors that reverses the situation in both KEs (blocking upstream KE will block downstream KE).</li>
</ul>
<ul>
<li>In an in vivo study it was indirectly shown that the microinjection to adult male Sprague Dawley rats of 10 μM DomA increased intracellular Ca2+ levels. A significant upregulation of phosphorylated calcium-calmodulin-dependent kinase II (CaMKII) and phosphorylated cAMP response element binding protein (CREB) levels was recorded, possibly due to increased intracellular Ca2+ levels induced by DomA (Qiu and Currás-Collazo, 2006).</li>
</ul>
<p>In CGNs, the co-treatment with 10 µM DomA and the kainate/AMPA receptor antagonist NBQX maintains Ca2+ levels near to control levels, suggesting that the Ca2+ elevation evoked by DomA is mediated by the activation of both AMPA/kainate and of NMDA receptors (Giordano et al., 2006).</p>
<p>The voltage-sensitive Ca2+ channel (VSCC) blocker nifedipine (5 μM) and NBQX (10 μM), a competitive AMPA/kainate receptor antagonist reduces the peak and final intracellular Ca2+ concentration in CGNs (Berman et al., 2002), strengthening the view that the increase of Ca2+ influx is not only mediated by NMDA receptors but also by AMPA/kainate receptors and VSCCs.</p>
<p> </p>
<p><span style="font-size:11.0pt"><span style="font-family:"Calibri",sans-serif">Table 1: Summary of available data describing responses of intracellular calcium to NMDA receptor activation. DA, DomA = Domoic Acid. Glu = Glutamate. NMDA = N-methyl-D-aspartate. The following are NMDA receptor (NMDAR) antagonists: D-AP5 = D-2-amino-5-phosphonopentanoate. MK-801 = Dizocilpine.</span></span></p>
<table border="1" cellspacing="0" style="border-collapse:collapse; font-size:75%">
<tbody>
<tr>
<td>
<p><strong>Stressor</strong></p>
</td>
<td>
<p><strong>Experimental Model</strong></p>
</td>
<td>
<p><strong>Tested concentrations</strong></p>
</td>
<td>
<p><strong>Exposure route</strong></p>
</td>
<td>
<p><strong>Exposure duration</strong></p>
</td>
<td>
<p><strong>Overactivation of NMDAR (KE up) (measurements, quantitative if available)</strong></p>
</td>
<td>
<p><strong>Increased intracelllular Ca 2+ levels (KE down) (measurements, quantitative if available)</strong></p>
</td>
<td>
<p><strong>References</strong></p>
</td>
<td>
<p><strong>Temporal Relationship</strong></p>
</td>
<td>
<p><strong>Dose-response relationship</strong></p>
</td>
<td>
<p><strong>Incidence</strong></p>
</td>
<td>
<p><strong>Comments</strong></p>
</td>
</tr>
<tr>
<td>
<p>DomA</p>
</td>
<td>
<p>Mouse cerebellar granule neurons (CGNs) from Gclm (+/+) and Gclm (−/−) mice</p>
</td>
<td>
<p>0.01 to 10 µM</p>
</td>
<td>
<p> </p>
</td>
<td>
<p>Time course (15 to 120 min)</p>
</td>
<td>
<p> </p>
</td>
<td>
<p>5 and 8 fold increase of [Ca2+]i compared to controls.</p>
</td>
<td>
<p>Giordano et al., 2006</p>
</td>
<td>
<p> </p>
</td>
<td>
<p> </p>
</td>
<td>
<p> </p>
</td>
<td>
<p>The cells were exposed simultaneously to DA and the NMDA receptor antagonist MK-801 and the Ca2+ levels were found to be close to control levels, indicating that the Ca2+ elevation evoked by DA involves activation of NMDA receptors.</p>
</td>
</tr>
<tr>
<td>
<p>DomA</p>
</td>
<td>
<p>CGNs from Gclm (+/+) and Gclm (−/−) mice</p>
</td>
<td>
<p>0.01 to 10 µM</p>
</td>
<td>
<p> </p>
</td>
<td>
<p>Time course (0 to 25 min)</p>
</td>
<td>
<p> </p>
</td>
<td>
<p>0.1μM domoic acid caused a small and delayed increase (4 fold) in [Ca2+]i, with a full recovery by 20 min.In contrast, the higher concentration of domoic acid (10μM) caused a rapid and robust increase (8 fold) in [Ca2+]i, which was still elevated after 25 min.</p>
<p>0.1μM DA increases [Ca2+]M by about 3 fold, with a delay of about 15 min. In contrast, no changes in [Ca2+]M were observed following 10μM of DA.</p>
</td>
<td>
<p>Giordano et al., 2007</p>
</td>
<td>
<p> </p>
</td>
<td>
<p> </p>
</td>
<td>
<p> </p>
</td>
<td>
<p>At the low concentration (0.1μM), the recording of intracellular Ca2+ was antagonized only by NBQX (AMPA receptor antagonist), but not by MK-801 (NMDA receptor antagonist). On the other hand, the higher DA concentration (10μM) caused a rapid and robust increase in intracellular Ca2+ . This effect was antagonized by both NBQX and MK-801, suggesting the importance of NMDA receptors in Ca2+ elevation evoked by DA but only at high doses</p>
</td>
</tr>
<tr>
<td>
<p>DomA</p>
</td>
<td>
<p>10-13 DIV CGNs obtained from 8-day-old Sprague–Dawley rats</p>
</td>
<td>
<p>0.1 to 30 µM</p>
</td>
<td>
<p> </p>
</td>
<td>
<p>Time course (0 to 45 min)</p>
</td>
<td>
<p> </p>
</td>
<td>
<p>EC50 for DA-induced increase in intracellular Ca2+ was 0.61 μM</p>
</td>
<td>
<p>Berman et al., 2002</p>
</td>
<td>
<p> </p>
</td>
<td>
<p> </p>
</td>
<td>
<p> </p>
</td>
<td>
<p>The NMDA receptor antagonist MK-801 significantly reduced both peak and final plateau of intracellular Ca2+ by 30 and 70%, respectively</p>
</td>
</tr>
<tr>
<td>
<p>DomA</p>
</td>
<td>
<p>Adult male Sprague Dawley rats</p>
</td>
<td>
<pre>
10 µM
</pre>
</td>
<td>
<p>Brain microinjection</p>
</td>
<td>
<p> </p>
</td>
<td>
<p> </p>
</td>
<td>
<p>Increased phosphorylated CaMKII and phosphorylated CREB levels</p>
</td>
<td>
<p>Qiu and Currás-Collazo, 2006</p>
</td>
<td>
<p> </p>
</td>
<td>
<p> </p>
</td>
<td>
<p> </p>
</td>
<td>
<p> </p>
</td>
</tr>
<tr>
<td><span style="font-size:8.0pt"><span style="font-family:"Arial",sans-serif">Glutamate, NMDA</span></span></td>
<td><span style="font-size:8.0pt"><span style="font-family:"Arial",sans-serif">Mouse cortical astrocytes</span></span></td>
<td><span style="font-size:8.0pt"><span style="font-family:"Arial",sans-serif">Glutamate: 100 µM<br />
NMDA: 20 µM</span></span></td>
<td> </td>
<td><span style="font-size:8.0pt"><span style="font-family:"Arial",sans-serif">Brief (1s application)</span></span></td>
<td> </td>
<td><span style="font-size:8.0pt"><span style="font-family:"Arial",sans-serif">Increased intracellular Ca2+ measured through Fluo-3 Flourescence</span></span></td>
<td><span style="font-size:8.0pt"><span style="font-family:"Arial",sans-serif">Palygin et al., 2011</span></span></td>
<td> </td>
<td> </td>
<td> </td>
<td><span style="font-size:8.0pt"><span style="font-family:"Arial",sans-serif">Provides time-series data of intracellular calcium measured through fluoresence given an application of Glu, NMDA, or Glu + D-AP5 in mouse cortical astrocytes. Cells were additionally exposed to D-AP5, an NMDA antagonist, and showed reduced fluorscence changes. (added by DS for AOP 281)</span></span></td>
</tr>
<tr>
<td><span style="font-size:8.0pt"><span style="font-family:"Arial",sans-serif">Glutamate</span></span></td>
<td><span style="font-size:8.0pt"><span style="font-family:"Arial",sans-serif">Cultured rat hippocampal neurons</span></span></td>
<td><span style="font-size:8.0pt"><span style="font-family:"Arial",sans-serif">500 µM</span></span></td>
<td> </td>
<td><span style="font-size:8.0pt"><span style="font-family:"Arial",sans-serif">Time course (0 to 45 minutes)</span></span></td>
<td> </td>
<td><span style="font-size:8.0pt"><span style="font-family:"Arial",sans-serif">Increased intracellular Ca2+ measured through Fura-2 Flourescence</span></span></td>
<td><span style="font-size:8.0pt"><span style="font-family:"Arial",sans-serif">Michaels and Rothman, 1990</span></span></td>
<td> </td>
<td> </td>
<td> </td>
<td><span style="font-size:8.0pt"><span style="font-family:"Arial",sans-serif">Provides time-series data of intracellular calcium measured through fluoresence, as well as directly providing calculated intracellular calcium concentrations in response to high concentrations of applied Glu, both alone and with antagonists. (added by DS for AOP 281)</span></span></td>
</tr>
<tr>
<td><span style="font-size:8.0pt"><span style="font-family:"Arial",sans-serif">NMDA, Glutamate</span></span></td>
<td><span style="font-size:8.0pt"><span style="font-family:"Arial",sans-serif">Neocortical neurons of Swiss-Webster mice</span></span></td>
<td><span style="font-size:8.0pt"><span style="font-family:"Arial",sans-serif">Glutamate: 300 µM<br />
NMDA: 300 µM</span></span></td>
<td> </td>
<td><span style="font-size:8.0pt"><span style="font-family:"Arial",sans-serif">Time course (0 to 20 minutes) and (0 to 2 minutes)</span></span></td>
<td> </td>
<td><span style="font-size:8.0pt"><span style="font-family:"Arial",sans-serif">Increased intracellular Ca2+ measured through Fura-2/AM, Fura-2/K+, Fura-2/dextran, BTC</span></span></td>
<td><span style="font-size:8.0pt"><span style="font-family:"Arial",sans-serif">Hyrc et al., 1997</span></span></td>
<td> </td>
<td> </td>
<td> </td>
<td><span style="font-size:8.0pt"><span style="font-family:"Arial",sans-serif">Provides time-series data of intracellular calcium measured through a variety of fluorsence calcium indicators given an application of the selective agonist NMDA. </span></span><span style="font-size:8.0pt"><span style="font-family:"Arial",sans-serif">(added by DS for AOP 281)</span></span></td>
</tr>
<tr>
<td><span style="font-size:8.0pt"><span style="font-family:"Arial",sans-serif">Glutamate</span></span></td>
<td><span style="font-size:8.0pt"><span style="font-family:"Arial",sans-serif">Computational model (CA1 pyramidal neuron)</span></span></td>
<td> </td>
<td> </td>
<td> </td>
<td> </td>
<td><span style="font-size:8.0pt"><span style="font-family:"Arial",sans-serif">Models the concentration of Ca2+ in spine(s) of neuron</span></span></td>
<td><span style="font-size:8.0pt"><span style="font-family:"Arial",sans-serif">Hu et al., 2018</span></span></td>
<td> </td>
<td> </td>
<td> </td>
<td><span style="font-size:8.0pt"><span style="font-family:"Arial",sans-serif">Developed a computational model of a glutamatergic spine which models intracellular calcium dynamics and sources of calcium influx including activation of NMDA receptors. </span></span><span style="font-size:8.0pt"><span style="font-family:"Arial",sans-serif">(added by DS for AOP 281)</span></span></td>
</tr>
</tbody>
</table>
<p> </p>
<p><strong>Glufosinate (GLF)</strong></p>
<p>There are no data showing that an exposure to GLF causes an increase in intra-cellular calcium. Such assumption can be proposed based on a fact that GLF directly activates NMDR as described in the MIE and other relevant KEs of this AOP.</p>
<p>A case of a 59-yr-old woman who ingested a herbicide containing glufosinate was suffering from severe intoxication, however, she did not develop convulsions, which experimentally occurs in rats treated with GLF (Koyama et al., 1994) and is described in other human cases (Watanabe and Sano 1998).</p>
<p><em>Is it known how much change in the first event is needed to impact the second? Are there known modulators of the response-response relationships? Are there models or extrapolation approaches that help describe those relationships? </em></p>
<p>The experiments describing semi-quantitative effects for these KERs are described in the table above.</p>
HighUnspecificHighAll life stagesLowHighHigh<p><span style="font-size:12pt"><span style="font-family:Calibri,sans-serif"><span style="font-size:11.0pt"><span style="font-family:"Helvetica Neue""><span style="color:black">NMDARs have been shown to regulate calcium ion flow in a variety of species including zebrafish and rats </span></span></span><span style="font-size:11.0pt"><span style="font-family:"Helvetica Neue""><span style="color:black">(Horzmann and Freeman, 2016, el Nasr et al., 1990)</span></span></span><span style="font-size:11.0pt"><span style="font-family:"Helvetica Neue""><span style="color:black">.</span></span></span></span></span></p>
<p><br />
Berman FW, LePage KT, Murray TF., Domoic acid neurotoxicity in cultured cerebellar granule neurons is controlled preferentially by the NMDA receptor Ca(2+) influx pathway. Brain Res., 2002, 924: 20-29.</p>
<p><span style="font-size:12pt"><span style="font-family:Calibri,sans-serif">el Nasr, M. S., Peruche, B., Roβberg, C., Mennel, H.-D. & Krieglstein, J. 1990. Neuroprotective effect of memantine demonstrated in vivo and in vitro. <em>European Journal of Pharmacology,</em> 185<strong>,</strong> 19-24. DOI: <a href="https://doi.org/10.1016/0014-2999(90)90206-L" style="color:blue; text-decoration:underline">https://doi.org/10.1016/0014-2999(90)90206-L</a>.</span></span></p>
<p>Faro LR, Ferreira Nunes BV, Alfonso M, Ferreira VM, Durán R., Role of glutamate receptors and nitric oxide on the effects of glufosinate ammonium, an organophosphate pesticide, on in vivo dopamine release in rat striatum. Toxicology., 2013, Sep 15, 311: 154-61.</p>
<p>Giordano G, White CC, McConnachie LA, Fernandez C, Kavanagh TJ, Costa LG., Neurotoxicity of domoic Acid in cerebellar granule neurons in a genetic model of glutathione deficiency. Mol Pharmacol. 2006., 70: 2116-2126.</p>
<p>Giordano G, White CC, Mohar I, Kavanagh TJ, Costa LG., Glutathione levels modulate domoic acid-induced apoptosis in mouse cerebellar granule cells. Toxicol Sci., 2007, 100: 433-444.</p>
<p>Higley MJ, Sabatini BL., Calcium signalling in dendritic spines. Cold Spring Harb Perspect Biol., 2012, 4: a005686.</p>
<p><span style="font-size:12pt"><span style="font-family:Calibri,sans-serif">Horzmann, K. A. & Freeman, J. L. 2016. Zebrafish get connected: investigating neurotransmission targets and alterations in chemical toxicity. <em>Toxics,</em> 4. </span></span></p>
<p><span style="font-size:12pt"><span style="font-family:Calibri,sans-serif">Hu, E., Mergenthal, A., Bingham, C. S., Song, D., Bouteiller, J. M. & Berger, T. W. 2018. A Glutamatergic Spine Model to Enable Multi-Scale Modeling of Nonlinear Calcium Dynamics. <em>Front Comput Neurosci,</em> 12<strong>,</strong> 58. DOI: 10.3389/fncom.2018.00058.</span></span></p>
<p><span style="font-size:12pt"><span style="font-family:Calibri,sans-serif">Hyrc, K., Handran, S. D., Rothman, S. M. & Goldberg, M. P. 1997. Ionized intracellular calcium concentration predicts excitotoxic neuronal death: observations with low-affinity fluorescent calcium indicators. <em>J Neurosci,</em> 17<strong>,</strong> 6669-77. DOI: 10.1523/jneurosci.17-17-06669.1997.</span></span></p>
<p>Koyama K, Andou Y, Saruki K, Matsuo H., Delayed and severe toxicities of a herbicide containing glufosinate and a surfactant. Vet Hum Toxicol., 1994, 36: 17-8.</p>
<p>Lantz Stephen R , Cina M. Mack , Kathleen Wallace, Ellen F. Key , Timothy J. Shafer , John E. Casida., Glufosinate binds N-methyl-D aspartate receptors and increases neuronal network activity in vitro. NeuroToxicology, 2014, 45: 38–47.</p>
<p>Lefebvre KA, Robertson A. Domoic acid and human exposure risks: a review. Toxicon. 2010 Aug 15;56(2):218-30.</p>
<p>Liu F, Patterson TA, Sadovova N, Zhang X, Liu S, Zou X, Hanig JP, Paule MG, Slikker W Jr, Wang C., Ketamine-induced neuronal damage and altered N-methyl-D-aspartate receptor function in rat primary forebrain culture. Toxicol Sci., 2013, 131: 548-557.</p>
<p>Luscher C. and Robert C. Malenka. NMDA Receptor-Dependent Long-Term Potentiation and Long-Term Depression (LTP/LTD). Cold Spring Harb Perspect Biol., 2012;4:a005710.</p>
<p>Matsumura N, Takeuchi C, Hishikawa K, Fujii T, Nakaki T., Glufosinate ammonium induces convulsion through N-methyl-D-aspartate receptors in mice. Neurosci Lett., 2001, 304(1-2): 123-5.</p>
<p><span style="font-size:12.0pt"><span style="font-family:"Calibri",sans-serif">Michaels, R. L. and Rothman, S. M. 1990. Glutamate neurotoxicity in vitro: antagonist pharmacology and intracellular calcium concentrations. <em>J Neurosci,</em> 10<strong>,</strong> 283-92. DOI: 10.1523/jneurosci.10-01-00283.1990.</span></span></p>
<p><span style="font-size:12.0pt"><span style="font-family:"Calibri",sans-serif">Palygin, O., Lalo, U. & Pankratov, Y. 2011. Distinct pharmacological and functional properties of NMDA receptors in mouse cortical astrocytes. <em>British Journal of Pharmacology,</em> 163<strong>,</strong> 1755-1766. DOI: 10.1111/j.1476-5381.2011.01374.x.</span></span></p>
<p>Qiu S, Currás-Collazo MC., Histopathological and molecular changes produced by hippocampal microinjection of domoic acid. Neurotoxicol Teratol., 2006, 28: 354-362.</p>
<p>Watanabe T, Sano T., Neurological effects of glufosinate poisoning with a brief review. Hum Exp Toxicol. 1998, 17: 35-9.</p>
2016-11-29T18:41:332023-09-10T20:11:55860a6895-936b-4295-8a97-a8a7ed2f68f912820d47-746d-49b4-8c7b-6ad40e68227f2023-10-18T01:22:232023-10-18T01:22:2312820d47-746d-49b4-8c7b-6ad40e68227f63649292-8c9e-410f-8ca9-65156b85feedHighUnspecificModerateDuring development and at adulthoodHighHighHigh2022-12-11T21:08:262022-12-11T21:08:2663649292-8c9e-410f-8ca9-65156b85feedc2145e3a-4959-49b9-ae23-12f43d7a300b2021-10-26T07:06:022021-10-26T07:06:02c2145e3a-4959-49b9-ae23-12f43d7a300bf61e9157-1c59-4f2c-b4f4-681da192aa04<p>Learning and memory is one of the outcomes of the functional expression of neurons and neural networks from mammalian to invertebrates. Damage or destruction of neurons by chemical compounds during development when they are in the process of synapses formation, integration and formation of neural networks, will derange the organization and function of these networks, thereby setting the stage for subsequent impairment of learning and memory. Exposure to the potential developmental toxicants during neuronal differentiation and synaptogenesis will increase risk of functional neuronal network damage leading to learning and memory impairment.</p>
<p>Impairments in learning and memory are measured using behavioral techniques. It is well accepted that these alterations in behavior are the result of structural or functional changes in neurocircuitry. Functional impairments are often measured using field potentials of critical synaptic circuits in hippocampus and cortex. A number of studies have been performed in rodent models that reveal deficits in both excitatory and inhibitory synaptic transmission in the hippocampus as a result of developmental thyroid insufficiency (Wang et al., 2012; Oerbeck et al., 2003; Wheeler et al., 2011; Wheeler et al., 2015; Willoughby et al., 2014; Davenport and Dorcey, 1972; Tamasy et al., 1986; Akaike, 1991; Axelstad et al., 2008; Gilbert and Sui, 2006; Gilbert et al., 2016; Gilbert, 2011; Gilbert et al., 2016). A well-established functional readout of memory at the synaptic level is known as long-term potentiation (LTP) (i.e., a persistent strengthening of synapses based on recent patterns of activity). Deficiencies in LTP are generally regarded as potential substrates of learning and memory impairments. In rodent models where synaptic function is impaired by TH deficiencies, deficits in hippocampus-mediated memory are also prevalent (Gilbert and Sui, 2006; Gilbert et al., 2016; Gilbert, 2011; Gilbert et al., 2016).</p>
<p>A number of studies have consistently reported alterations in synaptic transmission resulting from developmental TH disruption, and leading to decreased cognition.</p>
<p>Long-term potentiation (LTP) is a long-lasting increase in synaptic efficacy and its discovery suggested that changes in synaptic strength could provide the substrate for learning and memory (reviewed in Lynch, 2004). Moreover, LTP is intimately related to the theta rhythm, an oscillation long associated with learning. Learning-induced enhancement in neuronal excitability, a measurement of neural network function, has also been shown in hippocampal neurons following classical conditioning in several experimental approaches (reviewed in Saar and Barkai, 2003).</p>
<p>On the other hand, memory requires the increase in magnitude o<span style="font-size:16px"><span style="font-family:Arial,Helvetica,sans-serif">f excitatory postsynaptic currents (</span></span>EPSCs) to be developed quickly and to be persistent for few weeks at least without disturbing already potentiated contacts. Once again, a substantial body of evidence has demonstrated that tight connection between LTP and diverse instances of memory exist (reviewed in Lynch, 2004).</p>
<p>A review on Morris water maze (MWM) as a tool to investigate spatial learning and memory in laboratory rats also pointed out that the disconnection between neuronal networks rather than the brain damage of certain regions is responsible for the impairment of MWM performance. Functional integrated neural networks that involve the coordination action of different brain regions are consequently important for spatial learning and MWM performance<strong> </strong><span style="font-size:12px">(D'Hooge and De Deyn, 2001).</span></p>
<p>Moreover, it is well accepted that alterations in synaptic transmission and plasticity contribute to deficits in cognitive function. There are a number of studies that have linked exposure to TPO inhibitors (e.g., PTU, MMI), as well as iodine deficient diets, to changes in serum TH levels, which result in alterations in both synaptic function and cognitive behaviors (Akaike et al., 1991; Vara et al., 2002; Gilbert and Sui, 2006; Axelstad et al., 2008; Taylor et al., 2008; Gilbert, 2011; Gilbert et al., 2016), described in the indirect KER "Decrease of TH synthesis leads to learning and memory deficits".</p>
<p style="text-align:justify">Developmental hypothyroidism reduces the functional integrity in brain regions critical for learning and memory. Neurophysiological indices of synaptic transmission of excitatory and inhibitory circuitry are impaired in the hippocampus of hypothyroid animals. Both hippocampal regions (area CA1 and dentate gyrus) exhibit alterations in excitatory and inhibitory synaptic transmission following reductions in serum TH in the pre and early postnatal period (Vara et al., 2002; Sui and Gilbert, 2003; Sui et al., 2005; Gilbert and Sui, 2006; Taylor et al., 2008; Gilbert, 2011; Gilbert et al., 2016). These alterations persist into adulthood despite a recovery to euthyroid conditions in blood. The latter observation indicates that these alterations represent permanent changes in brain function caused by transient hormones insufficiencies induced during critical window of development. </p>
<p style="text-align:justify">Because the adult hippocampus is involved in learning and memory, it is a brain region of remarkable plasticity. Use-dependent synaptic plasticity is critical during brain development for synaptogenesis and fine tuning of synaptic connectivity. In the adult brain, similar plasticity mechanisms underlie use-dependency that underlies learning and memory, as exhibited in LTP model of synaptic memory. Hypothyroidism during development reduces the capacity for synaptic plasticity in juvenile and adult offspring (Vara et al., 2002; Sui and Gilbert, 2003; Dong et al., 2005; Sui et al., 2005; Gilbert and Sui, 2006; Taylor et al., 2008; Gilbert, 2011; Gilbert et al., 2016). Decrease of neuronal network function and plasticity are observed coincident with deficits in learning tasks that require the hippocampus.</p>
<p style="text-align:justify"><strong>- Wang et al., 2012: </strong>This study showed that maternal subclinical hypothyroidism impairs spatial learning in the offspring, as well as the efficacy and optimal time of T4 treatment in pregnancy. Female adult Wistar rats were randomly divided into six groups: control, hypothyroid (H), subclinical hypothyroid (SCH) and SCH treated with T4, starting from GD10, GD13 and GD17, respectively, to restore normal TH levels. Results indicate that progenies of SCH and H groups demonstrated significantly longer mean latency in the water maze test (on the 2<sup>nd</sup> training day, latency was ~83% higher in H group, and ~50% higher in SCH), and a lower amplification percentage of the amplitude (~15% lower in H group, and 12% lower in SCH), and slope of the field excitatory postsynaptic potential (fEPSP) recording (~20% lower in H group, and 17% lower in SCH), compared to control group. T4 treatment at GD10 and GD13 significantly shortened mean latency and increased the amplification percentage of the amplitude and slope of the fEPSPs of the progeny of rats with subclinical hypothyroidism. However, T4 treatment at GD17 showed only minimal effects on spatial learning in the offspring. Altogether these data indicate direct correlation between decrease of neural network function and learning and memory deficits.</p>
<p style="text-align:justify"><strong>- Liu et al., 2010 </strong>This study assessed the effects of hypothyroidism in 60 female rats who were divided into three groups: (i) maternal subclinical hypothyroidism (total thyroidectomy with T4 infusion), (ii) maternal hypothyroidism (total thyroidectomy without T4 infusion), and (iii) control (sham operated). The Morris water maze tests revealed that pups from the subclinical hypothyroidism group showed long-term memory deficits, and a trend toward short-term memory deficits.</p>
<p style="text-align:justify"><strong>- Gilbert and Sui, 2006 </strong>Administration of 3 or 10 ppm PTU to pregnant and lactating dams via the drinking water from GD6 until PND30 caused a 47% and 65% reduction in serum T4, in the dams of the low and high-dose groups, respectively. Baseline synaptic transmission was impaired in PTU-exposed animals: mean EPSP slope (by ~60% with 10 ppm PTU) and population spike amplitudes (by ~70% with 10 ppm PTU) in the dentate gyrus were reduced in a dose-dependent manner in adult offspring of PTU-treated dams. High-dose animals (10 ppm) demonstrated very little evidence of learning despite 16 consecutive days of training (~5-fold higher mean latency to find the hidden platform, used as an index of learning).</p>
<p style="text-align:justify"><strong>- Gilbert et al., 2016</strong> Exposure to PTU during development produced dose-dependent reductions in mRNA expression of nerve growth factor (Ngf) in whole hippocampus of neonates. These changes in basal expression persisted to adulthood despite the return to euthyroid conditions in blood. Developmental PTU treatment dramatically reduced the activity-dependent expression of neurotrophins and related genes in neonate hippocampus and was accompanied by deficits in hippocampal-based learning (e.g., mean latency to find a hidden platform, at 2<sup>nd</sup> trial resulted ~60% higher in rats treated with 10 ppm PTU).</p>
<p style="text-align:justify"><strong>- Gilbert, 2011</strong> Trace fear conditioning deficits to context and to cue reported in animals treated with PTU and who also displayed synaptic transmission and LTP deficits in hippocampus. Baseline synaptic transmission was impaired in PTU-exposed animals (by ~50% in animal treated with 3 ppm PTU). EPSP slope amplitudes in the dentate gyrus were reduced in a dose-dependent manner in adult offspring of PTU-treated dams.</p>
<p style="text-align:justify"> </p>
<p style="text-align:justify">BPA, an environmental toxicant known to inhibit NIS-mediated iodide uptake (Wu Y et al., 2016) has been found to cause learning and memory deficits in rodents as described below:</p>
<p style="text-align:justify">- <strong>Jang et al., 2012</strong> In this study, pregnant female C57BL/6 mice (F0) were exposed to BPA (0.1-10 mg/kg) from gestation day 6 to 17, and female offspring (F2) from F1 generation mice were analysed. Exposure of F0 mice to BPA (10 mg/kg) decreased hippocampal neurogenesis (~ 30% decrease of hippocampal BrdU<sup>+</sup> cells vs control) in F2 female mice. High-dose BPA (10 mg/kg) caused neurocognitive deficit (i.e., reduced memory retention) as shown by passive avoidance testing (~ 33% decrease vs control) in F2 mice. Furthermore, 10 mg/kg BPA decreased the hippocampal levels of BDNF (~ 35% lower vs control) in F2 mice. These results suggest that BPA exposure (NIS inhibitor) in pregnant mothers could decrease hippocampal neurogenesis (decreased number of neurons) and cognitive function in future generations.</p>
<p style="text-align:justify"> </p>
<p style="text-align:justify"><u>In humans</u>, the data linking these two specific KE are much more limited, but certainly clear reductions in IQ, with specific impairments in hippocampus-mediated functions have been observed.</p>
<p style="text-align:justify"><strong>- Wheeler et al., 2015</strong> This study assessed hippocampal functioning in adolescents with congenital hypothyroidism (CH), using functional magnetic resonance imaging (fMRI). 14 adolescents with CH and 14 typically developing controls (TDC) were studied. Hippocampal activation was greater for pairs than items in both groups, but this difference was only significant in TDC. When the groups were directly compared, the right anterior hippocampus was the primary region in which the TDC and CH groups differed for this pair memory effect. Results signify that adolescents with CH show abnormal hippocampal functioning during verbal memory processing, in order to compensate for the effects induced by TH deficit in the brain.</p>
<p style="text-align:justify"><strong>- Wheeler et al., 2012</strong> In this study hippocampal neuronal network function was measured based on synaptic performance using fMRI and was altered while subjects engaged in a memory task. Data showed paired word recognition deficits in adolescents with congenital hypothyroidism (N = 14; age range, 11.5-14.7 years) compared with controls (N = 15; age range, 11.2-15.5 years), with no impairment on simple word lists. Analysis of functional magnetic resonance imaging showed that adolescents with congenital hypothyroidism had both increased magnitude of hippocampal activation relative to controls and bilateral hippocampal activation when only the left was observed in controls. Furthermore, the increased activation in the congenital hypothyroidism group was correlated with the severity of the hypothyroidism experienced early in life.</p>
<p style="text-align:justify"><strong>- Willoughby et al., 2013</strong> Analogously, in this study, fMRI revealed increased hippocampus activation with word pair recognition task in CH and children born to women with hypothyroxinemia during midgestation. These differences in functional activation were not seen with single word recognition, but were revealed when retention of word pair associations was probed. The latter is a task requiring engagement of the hippocampus.</p>
<p style="text-align:justify">A series of important findings suggest that the biochemical changes that happen after induction of LTP also occur during memory acquisition, showing temporality between the two KEs (reviewed in Lynch, 2004).</p>
<p style="text-align:justify"><strong>- Morris et al., 1986</strong> This study found that blocking the NMDA receptor of the neuronal network with AP5 inhibits spatial learning in rats. Most importantly, in the same study they measured brain electrical activity and recorded that this agent also inhibits LTP, however, they have not proven that spatial learning and LTP inhibition are causally related.</p>
<p style="text-align:justify">Since then a number of NMDA receptor antagonists have been studied towards their ability to induce impairment of learning and memory. It is worth mentioning that similar findings have been found in human subjects:</p>
<p style="text-align:justify"><strong>- Grunwald et al., 1999</strong> By combining behavioural and electrophysiological data from patients with temporal lobe epilepsy exposed to ketamine, involvement of NMDA receptors in human memory processes was demonstrated.</p>
<p style="text-align:justify"> </p>
<p style="text-align:justify">The last KE preceding the AO (learning and memory deficits), i.e. "Decreased Neural Network Function", is also common to the AOP 13, entitled "Chronic binding of antagonist to N-methyl-D-aspartate receptors (NMDARs) during brain development induces impairment of learning and memory abilities" (<a href="https://aopwiki.org/aops/13">https://aopwiki.org/aops/13</a>). In this AOP 13, data on lead (Pb) exposure as reference chemical are reported. While these studies do not refer to TH disruption, they provide empirical support for the same KER described in the present AOP.</p>
<p style="text-align:justify"><strong>Pb2+:</strong> Exposure to low levels of Pb2+, during early development, has been implicated in long-lasting behavioural abnormalities and cognitive deficits in children (Needleman et al., 1975; Needleman and Gatsonis, 1990; Bellinger et al., 1991; 1992; Baghurst et al., 1992; Leviton et al., 1993; Needleman et al., 1996; Finkelstein et al., 1998; Lanphear et al., 2000; 2005; Canfield et al., 2003; Bellinger 2004; Lanphear et al., 2005; Surkan et al., 2007; Jusko et al., 2008; Neal and Guilarte, 2010) and experimental animals (Brockel and Cory-Slechta, 1998; Murphy and Regan, 1999; Moreira et al., 2001). Multiple lines of evidence suggest that Pb2+ can impair hippocampus-mediated learning in animal models (reviewed in Toscano and Guilarte, 2005).</p>
<p style="text-align:justify"><strong>- Jett et al., 1997</strong> Female rats exposed to Pb<sup>2+</sup> through gestation and lactation have shown more severe impairment of memory than male rats with similar Pb<sup>2+</sup> exposures.</p>
<p style="text-align:justify"><strong>- De Souza Lisboa et al., 2005</strong> This study reported that exposure to Pb<sup>2+ </sup>during both pregnancy and lactation caused depressive-like behaviour (detected in the forced swimming test) in female but not male rats.</p>
<p style="text-align:justify"><strong>- Anderson et al., 2012</strong> This study investigated the neurobehavioral outcomes in Pb<sup>2+</sup>-exposed rats (250, 750 and 1500 ppm Pb<sup>2+</sup> acetate in food) during gestation and through weaning and demonstrated that these outcomes are very much influenced by sex and rearing environment. In females, Pb<sup>2+</sup> exposure lessened some of the benefits of enriched environment on learning, whereas, in males, enrichment does help to overcome detrimental effects of Pb<sup>2+</sup> on learning. Regarding reference memory, environmental enrichment has not been beneficial in females when exposure to Pb<sup>2+</sup> occurs, in contrast to males.</p>
<p style="text-align:justify"><strong>- Jaako-Movits et al., 2005</strong> Wistar rat pups were exposed to 0.2% Pb<sup>2+</sup> via their dams' drinking water from PND 1 to PND 21 and directly via drinking water from weaning until PND 30. At PND 60 and 80, the neurobehavioural assessment has revealed that developmental Pb<sup>2+</sup> exposure induces persistent increase in the level of anxiety and inhibition of contextual fear conditioning. The same behavioural syndrome in rats has been described in Salinas and Huff, 2002.</p>
<p style="text-align:justify"><strong>- Finkelstein et al., 1998</strong> These observations are in agreement with observations on humans, as children exposed to low levels of Pb<sup>2+</sup> displayed attention deficit, increased emotional reactivity and impaired memory and learning.</p>
<p style="text-align:justify"><strong>- Kumar and Desiraju, 1992</strong> In Wistar rats fed with lead acetate (400 µg/g body weight/day) from PND 2 until PND 60, EEG findings showed statistically significant reduction in the delta, theta, alpha and beta band EEG spectral power in motor cortex and hippocampus, but not in delta and beta bands power of motor cortex in wakeful state. After 40 days of recovery, animals were assessed for their neurobehaviour, and revealed that Pb<sup>2+</sup> treated animals showed more time and sessions in attaining criterion of learning than controls.</p>
<p style="text-align:justify">Further data obtained using animal behavioral techniques demonstrate that NMDA mediated synaptic transmission is decreased by Pb<sup>2+</sup> exposure (Cory-Slechta, 1995; Cohn and Cory-Slechta, 1993 and 1994).</p>
<p style="text-align:justify"><strong>- Xiao et al., 2014</strong> Rat pups from parents exposed to 2 mM PbCl<sub>2</sub> three weeks before mating until their weaning (pre-weaning Pb<sup>2+</sup>) and weaned pups exposed to 2 mM PbCl<sub>2 </sub>for nine weeks (post-weaning Pb<sup>2+</sup>) were assessed for their spatial learning and memory by MWM on PND 85-90. The study revealed that both rat pups in pre-weaning Pb<sup>2+</sup> and post-weaning Pb<sup>2+</sup> groups performed significantly worse than those in the control group. The number of synapses in pre-weaning Pb<sup>2+</sup> group increased significantly, but it was still less than that of control group. The number of synapses in post-weaning Pb<sup>2+</sup> group was also less than that of control group, although the number of synapses had no differences between post-weaning Pb<sup>2+</sup> and control groups before MWM. In both pre-weaning Pb<sup>2+</sup> and post-weaning Pb<sup>2+</sup> groups, synaptic structural parameters such as thickness of postsynaptic density (PSD), length of synaptic active zone and synaptic curvature increased, whereas width of synaptic cleft decreased compared to controls.</p>
<p style="text-align:justify"><strong>The last KE preceding the AO (learning and memory deficits), i.e. "Decreased Neural Network Function", is also common to the AOP 17, entitled "</strong><strong> Binding of electrophilic chemicals to SH(thiol)-group of proteins and /or to seleno-proteins during brain development leads to impairment of learning and memory" (</strong><a href="https://aopwiki.org/aops/13"><strong>https://aopwiki.org/aops/17</strong></a><strong>). In this AOP 17, data on mercury exposure as reference chemical are reported. While these studies do not refer to TH disruption, they provide empirical support for the same KER described in the present AOP.</strong></p>
<p style="text-align:justify"><strong>Sokolowski et al. 2013</strong>. Rats at postnatal day 7 received a single injection of methylmercury (0.6 microgr/g, that caused caspase activation in the hilus of granule cell layer in hippocampus. At PD 21, a decrease in cell number or 22% in hilus and of 27% in granule cell layer, as well as a decreased proliferation of neural precursor cells of 25% were observed. This was associated with a decrease of spatial memory as assessed by Morris water maze.</p>
<p style="text-align:justify"><strong>Eddins et al., 2008</strong>. Mice exposed during postnatal week 1-3 to 2-5 mg/kg mercury chloride in 0.01 ml/g of NaCl injectd s.c. The behavioral tests at 3 months of age revealed learning deficits (radial maze), which was associated with increased levels of monoamines in frontal cortex.</p>
<p style="text-align:justify"><strong>Zanoli et al., 1994.</strong> Single injection of methylmercury (8 mg/kg by gavage) at gestational day 15. Offsprings analyzed at 14, 21, and 60 days of age exhibited a decrease in the number of muscarinic receptors at 14 and 21 days and a decrease in avoidance latency at 60 days, indicating learning and memory deficits.</p>
<p style="text-align:justify"><strong>Zanoli et al., 2001.</strong> Single injection of methylmercury (8 mg/kg) at gestational day 8. Brain was removed at PD 21 and 60. An increase in tryptophan level in hippocampus was detected at both days. At PD 21, a decrease in anthranilic acid and an increase in quinolinic acid was found. No change in glutamic acid nor in aspartic acid were detected.</p>
<p style="text-align:justify"><strong>Montgomery et al., 2008.</strong> C57/B6 mice exposed during pregnancy (GD 8-18) with food containing methylmercury (0.01 mg/kg body wheight). Tested when adult, they showed deficits in motor function, coordination, overall activity and impairment in reference memory.</p>
<p style="text-align:justify"><strong>Glover et al., 2009.</strong> Balb mice exposed to methylmercury in diet (low dose: 1.5 mg/kg; high dose: 4.5 mg/kg) during 11 weeks (6 weeks prior mating, 3 weeks during gestation and 2 weeks post-partum). Offsprings tested at PD 15 showed an accumulation of Hg in brain (0.08 mg/kg for low dose and 0.25 mg/kg for the high dose). At hte cellular level, there was alterations in gene expression for cytoskeleton, cell processes, cell adhesion, cell differentiation, development), which could be all involved in cellular network formation. This was associated with behavioral impairment, i.e. a decrease in exploratory activity measured in open field.</p>
<p style="text-align:justify"><strong>Onishchenko et al., 2007</strong>. Pregnant mice received 0.5 mg methylmercury/kg/day in drinking water from gestational dy 7 until day 7 after delivery. Offspring behavior was monitored at 5-15 and 26-36 weeks of age. Mercury-induced alterations in reference memory were detected.</p>
<p style="text-align:justify"><strong>Cagiano et al., 1990.</strong> Pregnant rat received at GD 15 8mg/kg of methylmercury by gavage. Offsprings were tested at day 16, 21 and 60. A reduced functional activity of glutamatergic system associated with disturbances in learning and memory were observed.</p>
<p style="text-align:justify"><strong>Rice, 1992.</strong> Female monkeys exposed to 10, 25 and 50 microg/kg/day to methylmercury. Male unexposed. Infants separated from mother at birth and exposed to similar doses did not show gross intellectual impairment, but interferences with temporal discrimination.</p>
<p style="text-align:justify"><strong>Sahin et al., 2016.</strong> Exposure of rat pups for 5 weeks or 5 months with mercury chloride (4.6 microg/kg as first injection, followed each day by 0.07 microg/kg/day). Learning and memory impairment measured by passive avoidance and Morris-water-maze was found in 5-weeks group, but not in the 5-month group. This was accompanied by hearing loss.</p>
<p style="text-align:justify"><strong>In humans:</strong></p>
<p style="text-align:justify"><strong>Orenstein et al., 2014. </strong>Maternal peripartum hair mercury level was measured to assess prenatal mercury exposure. The concentrations of mercury was found in the range of 0.3-5.1 microg/g, similar to fish eating population in US. However, statistical analyses revealed that each microg/g increase in hair Hg was associated with a decrement in visula memory, learning and verbal memory.</p>
<p style="text-align:justify"><strong>Yorifuji et al., 2011</strong>. A survey of the Minamata exposed population made in 1971 to assess pre- and post-natal exposure revealed a methylmercury-induced impairment of intelligence as well as behavioral dysfunction.</p>
<p>One of the most difficult issues for neuroscientists is to link neuronal network function to cognition, including learning and memory. It is still unclear what modifications of neuronal circuits need to happen in order to alter motor behaviour as it is recorded in a learning and memory test (Mayford et al., 2012), meaning that there is no clear understanding about how these two KEs are connected.</p>
<p style="text-align:justify">The direct relationship of alterations in neural network function and specific cognitive deficits is difficult to ascertain given the many forms that learning and memory can take and the complexity of synaptic interactions in even the simplest brain circuit. Linking of neurophysiological assessments to learning and memory processes have, by necessity, been made across simple monosynaptic connections and largely focused on the hippocampus. Alterations in synaptic function have been found in the absence of behavioral impairments. This may result from measuring only one component in the complex brain circuitry that underlies 'cognition', behavioral tests that are not sufficiently sensitive for the detection of subtle cognitive impairments, and behavioral plasticity whereby tasks are solved by the animal via different strategies developed as a consequence of developmental insult.</p>
<p style="text-align:justify">Finally, in order to provide empirical support for this KER, data on the effects of lead (Pb) exposure are reported. Several epidemiological studies where Pb2+ exposure levels have been studied in relation to neurobehavioural alterations in children have been reviewed in Koller et al. 2004. This review has concluded that in some occasions there is negative correlation between Pb2+ dose and cognitive deficits of the subjects due to high influence of social and parenting factors in cognitive ability like learning and memory (Koller et al. 2004), meaning that not always Pb2+ exposure is positively associated with learning and memory impairment in children.</p>
<p style="text-align:justify"><strong>Mercury</strong></p>
<p style="text-align:justify"><strong>Olczak et al., 2001. </strong>Postnatal exposure of rats to Thimerosal (4 injections with 12, 240, 1440 and 3000 microgHg/kg per injection). Effects were measured in adult, which exhibited alterations in dopaminergic system with decline in the density of striatal D2 receptors, with a higher sensitivity for males. No alterations in spatial learning and memory was observed, but impairments of motor activity, increased anxiety (open fiel measurment), which are other symptoms of autism spectrum disorder.</p>
<p style="text-align:justify"><strong>Franco et al., 2006.</strong> Lactational exposure of mice to methylmercury in drinking water (10 mg/L). Analysis at weaning revealed only impairment in motor performances.</p>
<p><strong>Franco et al., 2007.</strong> Lactational exposure of mice with mercury chloride (0.5 and 1.5 mg/kg, i.p. injection once a day).. At weaning , animals exhibited an increased level of mercury in cerebellum associated with motor deficit.</p>
<p style="text-align:justify"><strong>Cardenas et al., 2017</strong> showed that maternal red blood cell mercury of 3.8 ng/g was associated to increased DNA methylation of PON1 in umbilical cord blood only in male and observed deficit in cognitive performances, such as visual motor ability, vocabiary and verbal intellgence.</p>
<p>There is not enough quantitative information how much change decrease of neuronal network functions leads to learning and memory deficits. However, qualitatively is well documented that decrease of LTP is directly linked to learning and memory deficits.</p>
<p>There is very limited information on the degree of quantitative change in neural network function required to alter cognitive behaviors. This is a result of the diversity of methods for measuring both neuronal network function and learning and memory deficits, which hamper cross-study analyses. This highlights the need to develop empirical data based models of this KER. It is well known that the altered balance between excitatory and inhibitory synapses affects learning and memory, although no quantitative data are available.</p>
HighMixedHighDuring brain developmentHighHighHigh<p style="text-align:justify">Synaptic transmission and plasticity are achieved via mechanisms common across taxonomies. LTP has been recorded in aplysia, lizards, turtles, birds, mice, guinea pigs, rabbits and rats. Deficiencies in hippocampally based learning and memory following developmental hypothyroidism have been documented mainly in rodents and humans.</p>
<p style="text-align:justify">Akaike M, Kato, N., Ohno, H., Kobayashi, T. (1991). Hyperactivity and spatial maze learning impairment of adult rats with temporary neonatal hypothyroidism. Neurotoxicol Teratol 13:317-322.</p>
<p style="text-align:justify">Anderson DW, Pothakos K, Schneider JS. (2012). Sex and rearing condition modify the effects of perinatal lead exposure on learning and memory. Neurotoxicology 33: 985-995.</p>
<p style="text-align:justify">Axelstad M, Hansen PR, Boberg J, Bonnichsen M, Nellemann C, Lund SP, Hougaard KS, U H. (2008). Developmental neurotoxicity of Propylthiouracil (PTU) in rats: relationship between transient hypothyroxinemia during development and long-lasting behavioural and functional changes. Toxicol Appl Pharmacol 232:1-13.</p>
<p style="text-align:justify">Baghurst PA, Tong S, Sawyer MG, Burns J, McMichael AJ. (1992). Environmental exposure to lead and children’s intelligence at the age of seven years. The Port Pirie Cohort Study. N Engl J Med. 327: 1279-1284.</p>
<p style="text-align:justify">Bellinger D, Sloman J, Leviton A, Rabinowitz M, Needleman HL, Waternaux C. (1991). Low-level lead exposure and children's cognitive function in the preschool years. Pediatrics. 87: 219-227.</p>
<p style="text-align:justify">Bellinger DC, Stiles KM, Needleman HL. (1992). Low-level lead exposure, intelligence and academic achievement: a long-term follow-up study. Pediatrics. 90: 855-861.</p>
<p style="text-align:justify">Bellinger DC. (2004). Lead. Pediatrics 113: 1016-1022.</p>
<p style="text-align:justify">Brockel BJ, Cory-Slechta DA. (1998). Lead, attention, and impulsive behavior: changes in a fixed-ratio waiting-for-reward paradigm. Pharmacol Biochem Behav. 60: 545-552.</p>
<p style="text-align:justify">Cagiano, R., et al. (1990). "Evidence that exposure to methyl mercury during gestation induces behavioral and neurochemical changes in offspring of rats." Neurotoxicol Teratol <strong>12</strong>(1): 23-28.</p>
<p style="text-align:justify">Canfield RL, Henderson CR Jr, Cory-Slechta D, Cox C, Jusko TA, Lanphear BP. (2003). Intellectual impairment in children with blood lead concentrations below 10 μg per deciliter. N Engl J Med. 348: 1517-1526.</p>
<p style="text-align:justify">Cao X, Huang S, Ruan D. (2008). Enriched environment restores impaired hippocampal long-term potentiation and water maze performance induced by developmental lead exposure in rats. Dev Psychobiol. 50: 307-313.</p>
<p style="text-align:justify">Cardenas A, Rifas-Shiman SL, Agha G, Hivert MF, Litonjua AA, DeMeo DL, Lin X, Amarasiriwardena CJ, Oken E, Gillman MW, Baccarelli AA., Persistent DNA methylation changes associated with prenatal mercury exposure and cognitive performance during childhood., Sci Rep. 2017 Mar 21;7(1):288. doi: 10.1038/s41598-017-00384-5.</p>
<p style="text-align:justify">Cohn J, Cory-Slechta DA. (1993). Subsensitivity of lead-exposed rats to the accuracy-impairing and rate-altering effects of MK-801 on a multiple schedule of repeated learning and performance. Brain Res. 600: 208-218.</p>
<p style="text-align:justify">Cohn J, Cory-Slechta DA. (1994). Lead exposure potentiates the effects of N-methyl-D-asparate on repeated learning. Neurotoxicol Teratol. 16: 455-465.</p>
<p style="text-align:justify">Cory-Slechta DA. (1995). MK-801 subsensitivity following postweaning lead exposure. Neurotoxicology 16: 83-95.</p>
<p style="text-align:justify">de Souza Lisboa S F, Gonzalves G, Komatsu F, Salci Queiroz CA, Aparecido Almeida A, Gastaldello Moreira EN. (2005). Developmental lead exposure induces depressive-like behavior in female rats. Drug Chem Toxicol. 28: 67-77.</p>
<p style="text-align:justify">D'Hooge R, De Deyn PP. (2001). Applications of the Morris water maze in the study of learning and memory. Brain Res Brain Res Rev. 36: 60-90.</p>
<p style="text-align:justify">Dong J, Yin H, Liu W, Wang P, Jiang Y, Chen J. (2005). Congenital iodine deficiency and hypothyroidism impair LTP and decrease C-fos and C-jun expression in rat hippocampus. Neurotoxicology 26:417-426.</p>
<p style="text-align:justify">Eddins, D., et al. (2008). "Mercury-induced cognitive impairment in metallothionein-1/2 null mice." Neurotoxicol Teratol <strong>30</strong>(2): 88-95.</p>
<p style="text-align:justify">Finkelstein Y, Markowitz ME, Rosen JF. (1998). Low-level lead-induced neurotoxicity in children: an update on central nervous system effects. Brain Res Rev. 27: 168-176.</p>
<p style="text-align:justify">Franco, J. L., et al. (2006). "Cerebellar thiol status and motor deficit after lactational exposure to methylmercury." Environ Res <strong>102</strong>(1): 22-28.</p>
<p style="text-align:justify">Franco, J. L., et al. (2007). "Lactational exposure to inorganic mercury: evidence of neurotoxic effects." Neurotoxicol Teratol <strong>29</strong>(3): 360-367.</p>
<p style="text-align:justify">Gilbert ME, Kelly ME, Samsam TE, Goodman JH. (2005). Chronic developmental lead exposure reduces neurogenesis in adult rat hippocampus but does not impair spatial learning. Toxicol Sci. 86: 365-374.</p>
<p style="text-align:justify">Gilbert ME. (2011). Impact of low-level thyroid hormone disruption induced by propylthiouracil on brain development and function. Toxicol Sci 124:432-445.</p>
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2016-11-29T18:41:332022-07-15T08:41:5263649292-8c9e-410f-8ca9-65156b85feedf61e9157-1c59-4f2c-b4f4-681da192aa042022-12-11T21:08:512022-12-11T21:08:51Binding of chemicals to ionotropic glutamate receptors leads to impairment of learning and memory via loss of drebrin from dendritic spines of neuronsIGR binding leads to impairment of learning and memory (via loss of drebrin)<p><strong><span style="font-size:10.0pt"><span style="font-family:"Arial",sans-serif"><span style="color:black">Yuko Sekino<sup>1</sup>, Shihori Tanabe<sup>2</sup>, Noriko Koganezawa<sup>3</sup>, Tomoaki Shirao<sup>4</sup></span></span></span></strong></p>
<p><span style="font-size:11.0pt"><span style="font-family:"Arial",sans-serif">1 the University of Tokyo, Japan</span></span></p>
<p><span style="font-size:11.0pt"><span style="font-family:"Arial",sans-serif">2 National Institute of Health Sciences, Japan</span></span></p>
<p><span style="font-size:11.0pt"><span style="font-family:"Arial",sans-serif">3 Gunma University, Japan</span></span></p>
<p><span style="font-size:11.0pt"><span style="font-family:"Arial",sans-serif">4 AlzMed, Inc,, Japan</span></span></p>
Under development: Not open for comment. Do not citeUnder DevelopmentIncluded in OECD Work Plan1.107<div>
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<p style="text-align:justify"><span style="font-size:11pt"><span style="font-family:"Times New Roman",serif"><span style="font-family:"Arial",sans-serif">Neurotoxicity risk assessment is an important issue for regulatory agencies. Currently, chemicals with potential risks are determined by time-consuming and costly animal testing. Therefore, <em>in vitro</em> testing methods are needed to rapidly evaluate thousands of chemicals for which no safety data on neurotoxicity exist. In recent years, chemicals that induce learning and memory impairment are thought to increase the risk of neurodegenerative diseases such as Parkinson's disease and Alzheimer's disease. Therefore, such risk assessment is necessary for human safety. The existing AOP No. 6 in OECD Series on AOPs (AOP48 in the AOP-Wiki) defines a molecular initiating event (MIE) as “Binding of agonists to ionotropic glutamate receptors”, causing neuronal cell death linked to impairment of learning and memory through receptor hyperactivation<sup>(1)</sup>. </span></span></span></p>
<p style="text-align:justify"><span style="font-size:11pt"><span style="font-family:"Times New Roman",serif"><span style="font-family:"Arial",sans-serif">Recent studies have shown that synaptic dysfunction precedes neuronal death in the early stages of dementia accompanied with the neurodegenerative diseases. Synaptic dysfunction is presumed as a decrease in the number of dendritic spines in neurons of the cerebral cortex and hippocampus, which are essential for learning and memory<sup>(2)</sup>. Therefore, the risk for impairment of learning and memory can be assessed by the synaptic dysfunction, namely decreased number of dendritic spines<sup>(3)</sup>.</span></span></span></p>
<p style="text-align:justify"><span style="font-size:11pt"><span style="font-family:"Times New Roman",serif"><span style="font-family:"Arial",sans-serif">Dendritic spines are small actin-rich projections protruding from the dendrites of neurons that form excitatory synapses in the cortex and hippocampus<sup>(4)</sup>. Drebrin is an actin-binding protein that localizes to dendritic spines and is said to play a specific role in their formation<sup>(5)</sup>. Drebrin is known to decrease in Alzheimer's disease with a high correlation to symptom stage<sup>(6,7)</sup>. In low-density cultures of hippocampal neurons, the number of dendritic spines can be counted as the number of drebrin clusters with immunostaining. </span></span></span></p>
<p style="text-align:justify"><span style="font-size:11pt"><span style="font-family:"Times New Roman",serif"><span style="font-family:"Arial",sans-serif">We have developed an experimental protocol for low-density neuronal culture in 96-well plates and an algorithm that automatically counts the number of drebrin clusters by high-content imaging analysis<sup>(8)</sup>. These protocols have been shown to be useful for screening chemicals that bind to the NMDA receptor. In fact, we have examined the toxicity of phencyclidine (PCP) and PCP-analogues and published results in a paper<sup>(9)</sup>. We have developed not only the immunocytochemical protocol for <em>in vitro</em> assay using neuronal culture but also enzyme-linked immunosorbent assay (ELISA) kits to evaluate drebrin protein levels. Thus, decreased number of dendritic spines induced by chemicals can be assessed quantitatively as a loss of drebrin immunocytochemically and biochemically.</span></span></span></p>
<p style="text-align:justify"><span style="font-size:11pt"><span style="font-family:"Times New Roman",serif"><span style="font-family:"Arial",sans-serif">Here, we propose a new AOP with the same MIE as AOP No. 6, in which loss of drebrin as KE leads to impairment of learning and memory. Studies of genetically engineered mice have shown that <span style="color:red">drebrin deficiency is directly related to synaptic dysfunction and leads to the impairment of learning and memory</span>, <strong><u><span style="color:red">even in the absence of neuronal cell death</span></u></strong><sup>(10,11,12)</sup>. This is the most important distinction between the proposed AOP and the existing AOP. Measurement of drebrin expression levels in neurons with immunocytochemistry and/or ELISA is easy and high-reproducible. The new KE, loss of drebrin, will promote accumulation of data of chemicals for neurotoxicity. The proposed AOP is expected to contribute to the development of many <em>in vitro</em> test for neurotoxicity and to establish <em>in silico</em> prediction to evaluate safety of many substances for human and environments.</span></span></span></p>
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<p>Evidence for Chemical Initiation of this Molecular Initiating Event
</p><p>L-Glutamate and glycine (or D-serine) are endogenous agonists that bind to the LBD of specific NMDA receptor subunits. Here listed some known agonists for NMDA receptor, some of them are specific to the NR1 subunit and some others to the NR2 subunit (reviewed in Traynelis et al., 2010):
</p><p><b>Specific to NR1</b>
</p><p>Glycine,
l-Serine,
d-Serine,
l-Alanine,
d-Alanine,
d-Cycloserine,
HA 966, (+)-(1-hydroxy-3-aminopyrrolidine-2-one,)
β-Cl-d-Alanine,
β-F-dl-Alanine,
tri-F-dl-Alanine,
ACPC, 1-aminocyclopropane-1-carboxylic acid,
ACBC, 1-aminocyclobutane-1-carboxylic acid,
GLYX-13.
</p><p><b>Specific to NR2</b>
</p><p>l-Glutamate,
d-Glutamate,
l-Aspartate,
d-Aspartate,
N-Methyl-l-aspartate,
N-Methyl-d-aspartate,
SYM208,1
l-Homocysteinsulfinate,
d-Homocysteinsulfinate,
l-Homocysteate,
d-Homocysteate,
l-Cysteinesulfinate,
l-Cysteate,
d-Cysteate,
Homoquinolinate,
Ibotenate,
(R,S)-(Tetrazol-5-yl)glycine,
L-CCG-IV, (2S,3R,4S)-2-(carboxycyclopropyl)glycine,
trans-ACBD, trans-1-aminocyclobutane-1,3-dicarboxylate,
cis-ADA, cis-azetidine-2,4-dicarboxylic acid,
trans-ADC, azetidine-2,4-dicarboxylic acid,
cis-ACPD, (1R,3R)-aminocyclopentane-cis-dicarboxylate,
cis-2,3-Piperidinedicarboxylic acid,
(R)-NHP4G, 2-(N-hydroxylpyrazol-4-yl)glycine,
(R,S)-Ethyl-NHP5G, 2-(N-hydroxypyrazol-5-yl)glycine,
(R)-Propyl-NHP5G, 2-(N-hydroxypyrazol-5-yl)glycine.
</p><p><b>Domoic acid (DomA)</b> is structurally similar to kainic acid (KA) and both of them are analogues of the excitatory neurotransmitter L-glutamate. DomA induces excitotoxicity by an integrative action on ionotropic glutamate receptors at pre- and post-synaptic sides. DomA directly activates KA/AMPARs receptors followed by indirect activation of the NMDARs. Indeed, indirect activation of NMDARs by DomA is linked to the fact that KA and AMPA receptors activated by DomA induce increased levels of intracellular Ca2+ and Na+ which, in turn, causes endogenous glutamate release that subsequently potentiates activation of NMDARs (Berman and Murray, 1997; Berman et al., 2002; Watanabe et al., 2011). DomA has been demonstrated through both in vitro and in vivo approaches to indirectly activate the NMDARs (reviewed in Pulido et al., 2008).
</p><p><b>Glufosinate (GLF)</b>((RS)-2-amino-4-(hydroxy(methyl)phosphonoyl)butanoic acid, phosphinothricin) is a phosphorus containing amino acid herbicide that is naturally occurring as a component of the bacteria-derived bactericidal and fungicidal tripeptides bialaphos and phosalacine (Lanz et al., 2014). There are studies suggesting that convulsive and amnesic effects of GLF are mediated through direct binding and activation of NMDAR (Lantz et al., 2014; Matsumura et al., 2001). GLF agonist action at the NMDAR is expected to occur through direct interaction with the glutamate binding site and requires binding of the glycine co-agonist as well as release of the magnesium block from the channel pore.
</p><p>A prime example of impairments in learning and memory as the adverse outcome for regulatory action is developmental lead exposure and IQ function in children (Bellinger, 2012). Most methods are well established in the published literature and many have been engaged to evaluate the effects of developmental thyroid disruption. The US EPA and OECD Developmental Neurotoxicity (DNT) Guidelines (OCSPP 870.6300 or OECD TG 426) <span style="font-size:16px"><span style="font-family:Arial,Helvetica,sans-serif">as well as OECD TG 443 (OECD, 2018)</span></span> both require testing of learning and memory (USEPA, 1998; OECD, 2007) advising to use the following tests passive avoidance, delayed-matching-to-position for the adult rat and for the infant rat, olfactory conditioning, Morris water maze, Biel or Cincinnati maze, radial arm maze, T-maze, and acquisition and retention of schedule-controlled behaviour. These DNT Guidelines have been deemed valid to identify developmental neurotoxicity and adverse neurodevelopmental outcomes (Makris et al., 2009).</p>
<p>Also, in the frame of the OECD GD 43 (2008) on reproductive toxicity, learning and memory testing may have potential to be applied in the context of developmental neurotoxicity studies. However, many of the learning and memory tasks used in guideline studies may not readily detect subtle impairments in cognitive function associated with modest degrees of developmental thyroid disruption (Gilbert et al., 2012).</p>
adjacentModerateHighadjacentNot SpecifiedNot SpecifiedadjacentNot SpecifiedNot SpecifiedadjacentHighHighadjacentNot SpecifiedNot SpecifiedadjacentNot SpecifiedNot SpecifiedadjacentModerateHighnon-adjacentModerateModerate<ol>
<li style="text-align:justify"><span style="font-size:11pt"><span style="font-family:"Times New Roman",serif"><span style="font-family:"Arial",sans-serif">Adverse Outcome Pathway on binding of agonists to ionotropic glutamate receptors in adult brain leading to excitotoxicity that mediates neuronal cell death, contributing to learning and memory impairment, Sachana M, et al. OECD Series on Adverse Outcome Pathways (2016)</span><em> </em><span style="font-family:"Arial",sans-serif">No. 6, OECD Publishing, Paris, doi: 10.1787/5jlr8vqgm630-en.</span></span></span></li>
<li style="text-align:justify"><span style="font-size:11pt"><span style="font-family:"Times New Roman",serif"><span style="font-family:"Arial",sans-serif">Synapse pathology in Alzheimer’s disease, Griffiths J, Grant GN. </span><span style="font-family:"Arial",sans-serif"><span style="color:#2e2e2e">Seminars in Cell and Developmental Biology </span></span><span style="font-family:"Arial",sans-serif">(</span><span style="font-family:"Arial",sans-serif"><span style="color:#2e2e2e">2022) </span></span><span style="font-family:"Arial",sans-serif">doi: 10.1016/j.semcdb.2022.05.028.<span style="color:#2e2e2e"> (review)</span></span></span></span></li>
<li style="text-align:justify"><span style="font-size:11pt"><span style="font-family:"Times New Roman",serif"><span style="font-family:"Arial",sans-serif"><span style="color:#2e2e2e">Dopamine Restores Limbic Memory Loss, Dendritic Spine Structure, and NMDAR-Dependent LTD in the Nucleus Accumbens of Alcohol-Withdrawn Rats Cannizzaro C, et al. J Neurosci. (2019) Jan 30;39(5):929-943. doi: 10.1523/JNEUROSCI.1377-18.2018.</span></span></span></span></li>
<li style="text-align:justify"><span style="font-size:11pt"><span style="font-family:"Times New Roman",serif"><span style="font-family:"Arial",sans-serif">Actin in dendritic spines: connecting dynamics to function,</span><span style="font-family:"Arial",sans-serif"><span style="color:#2e2e2e"> Hotulainen P, Hoogenraad C. J Cell Biol (2010) 17;189(4):619-29. doi: 10.1083/jcb. 201003008. (review)</span></span> </span></span></li>
<li style="text-align:justify"><span style="font-size:11pt"><span style="font-family:"Times New Roman",serif"><span style="font-family:"Arial",sans-serif"><span style="color:#2e2e2e">Role of actin cytoskeleton in dendritic spine morphogenesis. </span></span><span style="font-family:"Arial",sans-serif"><span style="color:#2e2e2e">Sekino Y, et al. Neurochem Int. (2007) 51(2-4):92-104. doi: 10.1016/j.neuint.2007.04.029. (review)</span></span></span></span></li>
<li style="text-align:justify"><span style="font-size:11pt"><span style="font-family:"Times New Roman",serif"><span style="font-family:"Arial",sans-serif"><span style="color:#2e2e2e">Drebrin, a dendritic spine protein, is manifold decreased in brains of patients with Alzheimer’s disease and Down syndrome </span></span><span style="background-color:white"><span style="font-family:"Arial",sans-serif"><span style="color:#212121">Shim KS, Lubec G.</span></span></span><span style="font-family:"Arial",sans-serif"><span style="color:#2e2e2e"> Neurosci Lett. 2002 May 24;324(3):209-12. doi: 10.1016/s0304-3940(02)00210-0.</span></span></span></span></li>
<li style="text-align:justify"><span style="font-size:11pt"><span style="font-family:"Times New Roman",serif"><span style="font-family:"Arial",sans-serif"><span style="color:#2e2e2e">Differential expression of synaptic proteins in the frontal and temporal cortex of elderly subjects with mild cognitive impairment,</span></span> <span style="font-family:"Arial",sans-serif"><span style="color:#2e2e2e">Counts SE, et al. J Neuropathol Exp Neurol. 2006 Jun;65(6):592-601. doi: 10.1097/00005072-200606000-00007.</span></span></span></span></li>
<li style="text-align:justify"><span style="font-size:11pt"><span style="font-family:"Times New Roman",serif"><span style="font-family:"Arial",sans-serif"><span style="color:#2e2e2e">High-content imaging analysis for detecting the loss of drebrin clusters along dendrites in cultured hippocampal neurons Hanamura K, et al.</span></span><span style="font-family:"Arial",sans-serif"> <span style="color:#2e2e2e">J Pharmacol Toxicol Methods. (2019) 99:106607. doi: 10.1016/j.vascn.2019.106607.</span></span></span></span></li>
<li style="text-align:justify"><span style="font-size:11pt"><span style="font-family:"Times New Roman",serif"><span style="font-family:"Arial",sans-serif"><span style="color:#2e2e2e">Assessment of NMDA receptor inhibition of phencyclidine analogues using a high-throughput drebrin immunocytochemical assay Mitsuoka T, et al. J Pharmacol Toxicol Methods. (2019) 99:106583. doi: 10.1016/j.vascn.2019</span></span></span></span></li>
<li style="text-align:justify"><span style="font-size:11pt"><span style="font-family:"Times New Roman",serif"><span style="font-family:"Arial",sans-serif"><span style="color:#2e2e2e">Genetic disruption of the alternative splicing of drebrin gene impairs context-dependent fear learning in adulthood, </span></span><span style="background-color:white"><span style="font-family:"Arial",sans-serif"><span style="color:#212121">Kojima N, et al. Neuroscience. (2010) 165(1):138-50. Doi: 10.1016/j.neuroscience.2009.10.016.</span></span></span></span></span></li>
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