Inhibitory postsynaptic potential

Inhibitory postsynaptic potential

An Inhibitory Postsynaptic Potential (commonly abbreviated as IPSP) is the change in membrane voltage of a postsynaptic neuron which results from synaptic activation of inhibitory neurotransmitter receptors. The most common inhibitory neurotransmitters in the nervous system are GABA and glycine.

A postsynaptic potential is considered inhibitory when the resulting change in membrane voltage makes it more difficult for the cell to fire an action potential, lowering the firing rate of the neuron. They are the opposite of excitatory postsynaptic potentials (EPSPs), which result from the flow of ions like sodium into the cell.

Ionic basis of IPSP

At a typical inhibitory synapse the postsynaptic neural membrane permeability increases for positive potassium (K+) ions and/or negative chloride (Cl-) ions but not sodium (Na+) ions. This generally causes an influx of Cl- ions and/or efflux of K+ ions, thereby bringing the membrane potential closer to the equilibrium potential of these ions.

In addition IPSPs may be produced by closure of sodium or calcium channels. The permeability to Cl- of the GABA receptoror and glycine receptors produces IPSPs.

Sometimes increasing the amount of intracellular Chloride in relation to the extracellular chloride , will cause the IPSP to switch and become excitatory.

References

Dudel J., Voltage dependence of amplitude and time course of inhibitory synaptic current in crayfish muscle. Pflugers Arch. 1977 Oct 19;371(1-2):167-74.

Akasu T, Koketsu K., Electrogenesis of the slow inhibitory postsynaptic potential in bullfrog sympathetic ganglia. Jpn J Physiol. 1983;33(2):279-300.

White RL, Gardner D., Physostigmine prolongs the elementary event underlying decay of inhibitory postsynaptic currents in Aplysia. J Neurosci. 1983 Dec;3(12):2607-13.

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