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== How this Key Event works == | == How this Key Event works == | ||
− | In neuroscience, an excitatory postsynaptic potential (EPSP) is defined as | + | In neuroscience, an excitatory postsynaptic potential (EPSP) is defined as a neurotransmitter-induced postsynaptic potential change that depolarizes the cell, and hence increases the likelihood of initiating a postsynaptic action potential (Purves et al. 2001). On the contrary, an inhibitory postsynaptic potential (IPSP) decreases this likelihood. Whether a postsynaptic response is an EPSP or an IPSP depends on the type of channel that is coupled to the receptor, and on the concentration of permeant ions inside and outside the cell. In fact, the only factor that distinguishes postsynaptic excitation from inhibition is the reversal potential of the postsynaptic potential (PSP) in relation to the threshold voltage for generating action potentials in the postsynaptic cell. When an active presynaptic cell releases neurotransmitters into the synapse, some of them bind to receptors on the postsynaptic cell. Many of these receptors contain an ion channel capable of passing positively charged ions (e.g., Na+ or K+) or negatively charged ions (e.g., Cl-) either into or out of the cell. In epileptogenesis, discharges reduced GABA-A receptor-mediated hyperpolarizing IPSPs by shifting their reversal potentials in a positive direction. At the same time, the amplitudes of Schaffer collateral-evoked RS-α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor-mediated EPSPs and action potential-independent miniature EPSPs were enhanced, whereas N-methyl-d-aspartate receptor-mediated EPSPs remained unchanged. Together, these changes in synaptic transmission produce a sustained increase in hippocampal excitability (Lopantsev et al. 2009). |
== How it is Measured or Detected == | == How it is Measured or Detected == | ||
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Bromfield EB, Cavazos JE, Sirven JI. (2006) Chapter 1, Basic Mechanisms Underlying Seizures and Epilepsy. In: An Introduction to Epilepsy [Internet]. West Hartford (CT): American Epilepsy Society; Available from: http://www.ncbi.nlm.nih.gov/books/NBK2510/. | Bromfield EB, Cavazos JE, Sirven JI. (2006) Chapter 1, Basic Mechanisms Underlying Seizures and Epilepsy. In: An Introduction to Epilepsy [Internet]. West Hartford (CT): American Epilepsy Society; Available from: http://www.ncbi.nlm.nih.gov/books/NBK2510/. | ||
− | Dichter MA, Ayala GF. (1987) Cellular mechanisms of epilepsy: A status report. Science 237:157- | + | Dichter MA, Ayala GF. (1987) Cellular mechanisms of epilepsy: A status report. Science 237:157-64. |
− | + | Lopantsev V, Both M, Draguhn A. 2009. Rapid Plasticity at Inhibitory and Excitatory Synapses in the Hippocampus Induced by Ictal Epileptiform Discharges. Eur J Neurosci 29(6):1153–64. | |
− | + | Miura M, Yoshioka M, Miyakawa H, Kato H, Ito KI. (1997) Properties of calcium spikes revealed during GABAA receptor antagonism in hippocampal CA1 neurons from guinea pigs. J Neurophysiol. 78(5):2269-79. | |
+ | Purves D, Augustine GJ, Fitzpatrick D, Katz LC, LaMantia A-S, McNamara JO, Williams SM (Eds). 2001. Neuroscience. 2nd edition. Chapter 7. Neurotransmitter Receptors and Their Effects. Sunderland (MA): Sinauer Associates. Available from: http://www.ncbi.nlm.nih.gov/books/NBK10799/. | ||
<references /> | <references /> |
Latest revision as of 14:25, 23 June 2016
Contents
Event Title
Key Event Overview
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AOPs Including This Key Event
AOP Name | Event Type | Essentiality |
---|---|---|
Binding to the picrotoxin site of ionotropic GABA receptors leading to epileptic seizures | KE | Strong |
Taxonomic Applicability
Name | Scientific Name | Evidence | Links |
---|---|---|---|
mouse | Mus musculus | Strong | NCBI |
rat | Rattus norvegicus | Strong | NCBI |
guinea pig | Cavia porcellus | Strong | NCBI |
Level of Biological Organization
Biological Organization |
---|
Tissue |
How this Key Event works
In neuroscience, an excitatory postsynaptic potential (EPSP) is defined as a neurotransmitter-induced postsynaptic potential change that depolarizes the cell, and hence increases the likelihood of initiating a postsynaptic action potential (Purves et al. 2001). On the contrary, an inhibitory postsynaptic potential (IPSP) decreases this likelihood. Whether a postsynaptic response is an EPSP or an IPSP depends on the type of channel that is coupled to the receptor, and on the concentration of permeant ions inside and outside the cell. In fact, the only factor that distinguishes postsynaptic excitation from inhibition is the reversal potential of the postsynaptic potential (PSP) in relation to the threshold voltage for generating action potentials in the postsynaptic cell. When an active presynaptic cell releases neurotransmitters into the synapse, some of them bind to receptors on the postsynaptic cell. Many of these receptors contain an ion channel capable of passing positively charged ions (e.g., Na+ or K+) or negatively charged ions (e.g., Cl-) either into or out of the cell. In epileptogenesis, discharges reduced GABA-A receptor-mediated hyperpolarizing IPSPs by shifting their reversal potentials in a positive direction. At the same time, the amplitudes of Schaffer collateral-evoked RS-α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor-mediated EPSPs and action potential-independent miniature EPSPs were enhanced, whereas N-methyl-d-aspartate receptor-mediated EPSPs remained unchanged. Together, these changes in synaptic transmission produce a sustained increase in hippocampal excitability (Lopantsev et al. 2009).
How it is Measured or Detected
EPSPs are usually recorded using intracellular electrodes. See Miura et al. (1997) and Bromfield et al. (2006) for details.
Evidence Supporting Taxonomic Applicability
Miura et al. (1997) reported supporting evidence from guinea pigs whereas Dichter and Ayala (1987) and Bromfield et al. (2006) summarized relevant studies on humans.
References
Bromfield EB, Cavazos JE, Sirven JI. (2006) Chapter 1, Basic Mechanisms Underlying Seizures and Epilepsy. In: An Introduction to Epilepsy [Internet]. West Hartford (CT): American Epilepsy Society; Available from: http://www.ncbi.nlm.nih.gov/books/NBK2510/.
Dichter MA, Ayala GF. (1987) Cellular mechanisms of epilepsy: A status report. Science 237:157-64.
Lopantsev V, Both M, Draguhn A. 2009. Rapid Plasticity at Inhibitory and Excitatory Synapses in the Hippocampus Induced by Ictal Epileptiform Discharges. Eur J Neurosci 29(6):1153–64.
Miura M, Yoshioka M, Miyakawa H, Kato H, Ito KI. (1997) Properties of calcium spikes revealed during GABAA receptor antagonism in hippocampal CA1 neurons from guinea pigs. J Neurophysiol. 78(5):2269-79.
Purves D, Augustine GJ, Fitzpatrick D, Katz LC, LaMantia A-S, McNamara JO, Williams SM (Eds). 2001. Neuroscience. 2nd edition. Chapter 7. Neurotransmitter Receptors and Their Effects. Sunderland (MA): Sinauer Associates. Available from: http://www.ncbi.nlm.nih.gov/books/NBK10799/.