Slowly-developing depolarization of neurones in the guinea-pig inferior mesenteric ganglion following repetitive stimulation of the preganglionic nerves.

Intracellular recordings were made from cells of the isolated guinea-pig inferior mesenteric ganglion. Stimulation of both hypogastric nerves at 30 Hz for 2 sec caused a slowly developing depolarization (SD) and fall in cell input resistance which reached a peak 10-30 sec after the end of stimulation. The amplitude of the SD was increased in a graded manner if the stimulus voltage was increased. The SD was unaffected by tubocurarine, atropine or guanethidine, but was blocked by removing external Ca. These results suggested that the SD was caused by the release of some substance from a large number of nerve terminals.