Mechanisms and Functions of Electrically Mediated Inhibition in the Vertebrate Central Nervous System
Although electrophysiologists have come to accept the concept that excitatory interactions between neurons can be mediated both electrically and chemically, it is generally assumed that inhibition is best carried out chemically (Bennett, 1972). Since inhibition generally results in a sign inversion, that is, depolarization of the presynaptic neuron leads to hyperpolarization of the postsynaptic element, it cannot commonly be mediated by electrotonic junctions. Exceptions under special conditions involve the preferential transmission of the spike after-hyperpolarization relative to the depolarizing phase of the action potential itself. In addition, this particular form of inhibition, which can be due to either a summation of after-hyperpolarizations during presynaptic firing (Tauc, 1969) or to a rectifying junction (Arvanitaki & Chalazonitis, 1959), results in a complex biphasic postsynaptic potential rather than in a pure hyperpolarization. Finally, it has been pointed out that these electrotonic junctions would favor excitatory transmission in the opposite direction (Arvanitaki & Chalazonitis, 1959).
KeywordsSpinal Cord Stimulation Intracellular Recording Lower Trace Eighth Nerve Axon Hillock
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