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inhibitory postsynaptic potential
An inhibitory postsynaptic potential (IPSP) is a kind of synaptic potential that makes a postsynaptic neuron less likely to generate an action potential.〔Purves et al. Neuroscience. 4th ed. Sunderland (MA): Sinauer Associates, Incorporated; 2008.〕 The opposite of an inhibitory postsynaptic potential is an excitatory postsynaptic potential (EPSP), which is a synaptic potential that makes a postsynaptic neuron ''more'' likely to generate an action potential. They can take place at all chemical synapses, which use the secretion of neurotransmitters to create cell to cell signalling. Inhibitory presynaptic neurons release neurotransmitters that then bind to the postsynaptic receptors; this induces a postsynaptic conductance change as ion channels open or close. An electric current that changes the postsynaptic membrane potential to create a more negative postsynaptic potential is generated. Depolarization can also occur due to an IPSP if the reverse potential is between the resting threshold and the action potential threshold. Another way to look at inhibitory postsynaptic potentials is that they are also a chloride conductance change in the neuronal cell because it decreases the driving force.Microelectrodes can be used to measure postsynaptic potentials at either excitatory or inhibitory synapses.
In general, a postsynaptic potential is dependent on the type and combination of receptor channel, reverse potential of the postsynaptic potential, action potential threshold voltage, ionic permeability of the ion channel, as well as the concentrations of the ions in and out of the cell; this determines if it is excitatory or inhibitory. IPSPs always want to keep the membrane potential more negative than the action potential threshold and can be seen as a “transient hyperpolarization”.〔Levy et al. Principles of Physiology. 4th ed. (PA): Elsevier; 2005.〕 EPSPs and IPSPs compete with each other at numerous synapses of a neuron; this determines whether or not the action potential at the presynaptic terminal will regenerate at the postsynaptic membrane. Some common neurotransmitters involved in IPSPs are GABA and glycine.
== Components ==
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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