Does cyclic GMP mediate the slow excitatory synaptic potential in sympathetic ganglia?

THE slow excitatory postsynaptic potential (slow EPSP) of vertebrate sympathetic ganglia is elicited by the muscarinic action of acetylcholine1,2. Its electrogenic mechanism appears strikingly different from that of the well-known (fast) EPSP in many respects—most notably that it is generated with no detectable increase in membrane conductance3. As this type of transmitter action is probably related to cholinergic processes in the brain4,5 and possibly in the spinal cord6, further study of the slow EPSP in the ganglia as a simpler model of the central cholinergic pathways is of great significance.

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