Intracellular recordings from vagally innervated intramural neurons in opossum stomach.

Intracellular recordings were made from intramural neurons in parafascicular ganglia in the opossum stomach. These ganglia were situated between the myenteric and subserosal plexuses and were found lying adjacent to vagal nerve fascicles. The neurons at these ganglia showed active and passive electrical properties similar only to S/type I enteric neurons. They received a complex innervation from preganglionic vagal fibers. These parasympathetic nerves elicited three distinct transmission processes in intramural neurons: fast and slow excitation (excitatory postsynaptic potentials, EPSP) and slow inhibition (inhibitory postsynaptic potential, IPSP). Fast EPSPs were cholinergically mediated via postjunctional nicotinic receptors, with convergence of numerous cholinergic fibers in several vagal fascicles to individual neurons. When seen, slow EPSPs increased neuronal excitability, whereas slow IPSPs decreased excitability.