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Event: 201

Key Event Title

A descriptive phrase which defines a discrete biological change that can be measured. More help

Binding of antagonist, NMDA receptors

Short name
The KE short name should be a reasonable abbreviation of the KE title and is used in labelling this object throughout the AOP-Wiki. More help
Binding of antagonist, NMDA receptors
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Biological Context

Structured terms, selected from a drop-down menu, are used to identify the level of biological organization for each KE. More help
Level of Biological Organization

Cell term

The location/biological environment in which the event takes place.The biological context describes the location/biological environment in which the event takes place.  For molecular/cellular events this would include the cellular context (if known), organ context, and species/life stage/sex for which the event is relevant. For tissue/organ events cellular context is not applicable.  For individual/population events, the organ context is not applicable.  Further information on Event Components and Biological Context may be viewed on the attached pdf. More help
Cell term

Organ term

The location/biological environment in which the event takes place.The biological context describes the location/biological environment in which the event takes place.  For molecular/cellular events this would include the cellular context (if known), organ context, and species/life stage/sex for which the event is relevant. For tissue/organ events cellular context is not applicable.  For individual/population events, the organ context is not applicable.  Further information on Event Components and Biological Context may be viewed on the attached pdf. More help

Key Event Components

The KE, as defined by a set structured ontology terms consisting of a biological process, object, and action with each term originating from one of 14 biological ontologies (Ives, et al., 2017; Biological process describes dynamics of the underlying biological system (e.g., receptor signalling).Biological process describes dynamics of the underlying biological system (e.g., receptor signaling).  The biological object is the subject of the perturbation (e.g., a specific biological receptor that is activated or inhibited). Action represents the direction of perturbation of this system (generally increased or decreased; e.g., ‘decreased’ in the case of a receptor that is inhibited to indicate a decrease in the signaling by that receptor).  Note that when editing Event Components, clicking an existing Event Component from the Suggestions menu will autopopulate these fields, along with their source ID and description.  To clear any fields before submitting the event component, use the 'Clear process,' 'Clear object,' or 'Clear action' buttons.  If a desired term does not exist, a new term request may be made via Term Requests.  Event components may not be edited; to edit an event component, remove the existing event component and create a new one using the terms that you wish to add.  Further information on Event Components and Biological Context may be viewed on the attached pdf. More help

Key Event Overview

AOPs Including This Key Event

All of the AOPs that are linked to this KE will automatically be listed in this subsection. This table can be particularly useful for derivation of AOP networks including the KE. Clicking on the name of the AOP will bring you to the individual page for that AOP. More help
AOP Name Role of event in AOP Point of Contact Author Status OECD Status
Binding of antagonist to NMDARs impairs cognition MolecularInitiatingEvent Anna Price (send email) Open for citation & comment WPHA/WNT Endorsed
Binding of antagonist to NMDARs can lead to neuroinflammation and neurodegeneration MolecularInitiatingEvent Florianne Tschudi-Monnet (send email) Open for citation & comment WPHA/WNT Endorsed

Taxonomic Applicability

Latin or common names of a species or broader taxonomic grouping (e.g., class, order, family) that help to define the biological applicability domain of the KE.In many cases, individual species identified in these structured fields will be those for which the strongest evidence used in constructing the AOP was available in relation to this KE. More help
Term Scientific Term Evidence Link
human Homo sapiens High NCBI
rat Rattus norvegicus High NCBI
mouse Mus musculus High NCBI

Life Stages

An indication of the the relevant life stage(s) for this KE. More help

Sex Applicability

An indication of the the relevant sex for this KE. More help

Key Event Description

A description of the biological state being observed or measured, the biological compartment in which it is measured, and its general role in the biology should be provided. More help

Biological state: 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.

Biological compartments: 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).

General role in biology: 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:

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).

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).

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).

How It Is Measured or Detected

A description of the type(s) of measurements that can be employed to evaluate the KE and the relative level of scientific confidence in those measurements.These can range from citation of specific validated test guidelines, citation of specific methods published in the peer reviewed literature, or outlines of a general protocol or approach (e.g., a protein may be measured by ELISA). Do not provide detailed protocols. More help

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? There is no OECD advised method for measuring NMDA receptor binding of antagonists. However, there are methods described in the scientific literature that allow measuring:

1. Ex vivo: The most common assay used is the NMDA receptor (MK801 site) radioligand competition binding assays (Reynolds, 2001; Gao et al., 2013;; 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).

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 (Korkut and Varnali, 2003; Koutsoukos et al., 2011; Gao et al., 2013; Mazumder and Borah, 2014; Chtitaa et al., 2015).

Domain of Applicability

A description of the scientific basis for the indicated domains of applicability and the WoE calls (if provided).  More help

The evolution of NMDAR subunits (NR1, NR2, NR3) is well-conserved throughout different species from lower organism to mammals, including humans (Ewald and Cline, 2009; Tikhonov and Magazanik, 2009; Koo and Hampson, 2010; Teng et al., 2010; Flores-soto et al., 2012).

Many of the binding sites for the noncompetitive or competitive antagonists e.g. for binding of dizocilpine (MK-801), phencyclidine, D-2-amino-5-phosphonopentanoate (AP5) and 3-((R)-2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid (R-CPP) are also conserved in Drosophila (reviewed in Xia and Chiang, 2009).

Cellular membranes can be prepared from different brain areas of distinct species. Using [3H]MK-801, high affinity binding sites for MK-801 were detected in membranes of the rat brain (Woodruff et al., 1987). The same binding assay has been used in preparations from human brains mostly from brain of patients with neurodegenerative disorders (Slater et al., 1993) as well as from brain of different marine, avian species (Scheuhammer et al., 2008) and insects (Eldefrawi et al., 1993).


List of the literature that was cited for this KE description. More help

Bale AS, Jackson MD, Krantz QT, Benignus VA, Bushnell PJ, Shafer TJ, Boyes WK. (2007) Evaluating the NMDA-glutamate receptor as a site of action for toluene, in vivo. Toxicol Sci. 98: 159-66.

Barria A, Malinow R. (2002) Subunit-specific NMDA receptor trafficking to synapses. Neuron 35: 345-353.

Chandrasekar R. (2013) Alcohol and NMDA receptor: current research and future direction. Front Mol Neurosci. 6: 14.

Chtitaa S, Larifb M, Ghamalia M, Bouachrinec M, Lakhlifia T. (2015) DFT-based QSAR Studies of MK801 derivatives for non competitive antagonists of NMDA using electronic and topological descriptors. Journal of Taibah University for Science. 9: 143-154.

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.

Eldefrawi ME, Anis NA, Eldefrawi AT. (1993) Glutamate receptor inhibitors as potential insecticides. Arch Insect Biochem Physiol. 22: 25-39.

Evans RH, Francis AA, Jones AW, Smith DA, Watkins JC. (1982) 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. 75: 65-75.

Ewald RC, Cline HT. (2009) Cloning and phylogentic analysis of NMDA receptor subunits NR1, NR2A and NR2B in Xenopus laevis tadpoles. Front Mol Neurosci. 2: 4.

Flores-soto ME, Chaparro-Huerta V, Escoto-Delgadillo M, Vazuez-Valls E, Gonzalez-Castaneda RE, Beas-Zarate C. (2012) Structure and function of NMDA-type glutamate receptor subunits. Neurologia 27: 301-310.

Gao L, Fang JS, Bai XY, Zhou D, Wang YT, Liu AL, Du GH. (2013) In silico Target Fishing for the Potential Targets and Molecular Mechanisms of Baicalein as an Antiparkinsonian Agent: Discovery of the Protective Effects on NMDA Receptor-Mediated Neurotoxicity. Chem Biol Drug Des. 81: 675-87.

Koo JCP, Hampson DR. (2010) Phylogenic and evolutionary analysis of glutamate receptor based on extant invertebrate genes. JULS 1: 42-48.

Korkut A, Varnali T. (2003) Quantitative structure activity relationship (QSAR) of competitive N-methyl-D-aspartate (NMDA) antagonists. Mol Phys 101: 3285-3291.

Koutsoukas A, Simms B, Kirchmair J, Bond PJ, Whitmore AV, Zimmer S, Young MP, Jenkins JL, Glick M, Glen RC, Bender A. (2011) From in silico target prediction to multi-target drug design: current databases, methods and applications. J Proteomics 74: 2554-2574.

Lovinger DM. (1995) Developmental decrease in ethanol inhibition of N-methyl-D-aspartate receptors in rat neocortical neurons: relation to the actions of ifenprodil. J Pharmacol Exp Ther. 274: 164-172.

Mazumder MK, Borah A. (2014) 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. Medical Hypotheses 83: 740–746.

Morris RJ. (1989) 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 9: 3040-3057.

Mugnaini M, van Amsterdam FT, Ratti E, Trist DG, Bowery NG. (1996) Regionally different N-methyl-D-aspartate receptors distinguished by ligand binding and quantitative autoradiography of [3H]-CGP 39653 in rat brain. Br J Pharmacol 119: 819–828.

Nagy J. (2008) Alcohol related changes in regulation of NMDA receptor functions. Curr Neuropharmacol 6: 39-54.

Neal AP, Guilarte TR. (2010) Molecular Neurobiology of Lead (Pb2+): Effects on Synaptic Function. Mol Neurobiol. 42: 151-160.

Neal AP. Worley PF. Guilarte TR (2011) Lead exposure during synaptogenesis alters NMDA receptor targeting via NMDA receptor inhibition. Neurotoxicology. 32:281-289.

Nihei MK, Guilarte TR. (1999) NMDAR-2A subunit protein expression is reduced in the hippocampus of rats exposed to Pb2+ during development. Brain Res Mol Brain Res. 66: 42-49.

Reynolds IJ. (2001) [3H](+)MK801 radioligand binding assay at the N-methyl-D-aspartate receptor. Curr Protoc Pharmacol. Chapter 1:Unit 1.20. doi: 10.1002/0471141755.ph0120s11.

Scheuhammer AM, Basu N, Burgess NM, Elliott JE, Campbell GD, Wayland M, Champoux L, Rodrigue J. (2008) Relationships among mercury, selenium, and neurochemical parameters in common loons (Gavia immer) and bald eagles (Haliaeetus leucocephalus). Ecotoxicology 17: 93-101.

Slater P, McConnell SE, D'Souza SW, Barson AJ. (1993) Postnatal changes in N-methyl-D-aspartate receptor binding and stimulation by glutamate and glycine of [3H]-MK-801 binding in human temporal cortex. Br J Pharmacol. 108: 1143-1149.

Smothers CT, Woodward JJ. (2007) Pharmacological characterization of glycine-activated currents in HEK 293 cells expressing N-methyl-d-aspartate NR1 and NR3 subunits. J Pharmacol Exp Ther. 322: 739-748.

Teng H, Cai W, Zhou L, Zhang J, Liu Q, Wang Y, et al. (2010) Evolutionary mode of functional divergence of vertebrate NMDA receptor subunit 2 Genes. PLoS ONE. 5(10): e13342.

Tikhonov DB, Magazanik LG. (2009) Origin and molecular evolution of ionotropic glutamate receptors. Neurosci Behav Physiol. 39: 763-772.

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.

Traynelis S, Wollmuth LP, McBain CJ, Menniti FS, Vance KM, Ogden KK, Hansen KB, Yuan H, Myers SJ, Dingledine R. (2010) Glutamate receptor ion channels: structure, regulation, and function. Pharmacol Rev. 62: 405-496.

Woodruff GN, Foster AC, Gill R, Kemp JA, Wong EH, Iversen LL. (1987) The interaction between MK-801 and receptors for N-methyl-D-aspartate: functional consequences. Neuropharmacology 26(7B): 903-909.

Xia S, Chiang AS. (2009) NMDA Receptors in Drosophila. In: Van Dongen AM, editor. Biology of the NMDA Receptor. Boca Raton (FL): CRC Press; Chapter 10. Available from: