Abstract
Publisher Summary A tremendous effort has been made to establish the multiplicity of synaptic transmitter substances for a single neuron and its synaptic endings. Ionotropic transmitter action occurs at special receptor sites on the postsynaptic membrane and rapidly opens ionic channels, so that there is a fast and large change in postsynaptic membrane conductance. In contrast, metabotropic transmitter action is effective postsynaptically by stimulating adenylate cyclase to give increased production of cyclic nucleotides with the consequent metabolic change in the postsynaptic cell by the second messenger system. There is overwhelming evidence that the emission of transmitter from the presynaptic terminals is quantal for the classical transmitters and that this quantal emission is due to the exocytosis of synaptic vesicles. The chapter illustrates a simple presynaptic feedback, noradrenalin inhibiting vesicular emission, and the varieties of transmitter interaction. Presynaptic feedbacks are postulated to be negative controls of transmitter release, especially the adenosine triphosphate (ATP) control of the purinergic, noradrenergic, and cholinergic nerve terminals.
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