Modulation of Presynaptic Transmitter Release by ATP Derived from Postsynaptic Sources
Both ATP and adenosine have long been known to be neurotransmitters released from presynaptio cells. However, ATP may also be released from stimulated postsynaptic cells. This has been observed in frog (1) and human (2) muscle as well as Torpedo electric organ (3). Moreover, exogenous ATP has been shown to reduce transmitter release from presynaptic terminals of preganglionic sympathetic neurons (4) and motoneurons (5). Likewise adenosine also depresses synaptic transmission in the central nervous system (6,7). One prime explanation for this phenomenon might be that Ca2+ entry into the terminals is somehow altered. However, this seems unlikely, because the depressant effect is independent of extracellular Ca2+ concentrations (7). Thus, some other mechanism must be involved, and it remains unknown.
KeywordsTransmitter Release Arginine Kinase Quantal Release Preganglionic Sympathetic Neuron Torpedo Electric Organ
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