Inhibitory cholinergic synapses in autonomic ganglia

Abstract

Slow synaptic potentials may provide mechanisms for long-term regulation of neuronal integration in the vertebrate nervous system. Autonomic ganglia, because of their structure and accessibility, have proved useful for studying several mechanisms of slow synaptic inhibition and excitation. Our purpose here is to review recent work on ganglionic slow inhibitory postsynaptic potentials (IPSPs). Although slow IPSPs are present in many ganglia, there is no consensus as to the transmitter(s) or ionic mechanism(s) that produce these responses. Furthermore, the ways in which slow IPSPs function physiologically to inhibit neuronal excitability have been largely a matter of speculation. Our recent experiments on sympathetic ganglia may serve to resolve controversies over mechanisms while also suggesting that interactions between slow cholinergic IPSPs and slow peptidergic excitatory postsynaptic potentials (EPSPs) function specifically to modulate the repetitive firing behavior of neurons.