ACTIONS OF SUBSTANCE-P ON SYMPATHETIC NEURONS

When applied to the neurons of isolated inferior mesenteric ganglia of guinea pig, substance P consistently caused a membrane depolarization accompanied, in many instances, by intense neuronal discharges. The substance P-induced depolarization or spikings were not abolished by d-tubocurarine and/or atropine or by superfusing the ganglia with a low Ca/high Mg solution. Repetitive stimulation of hypogastric nerves elicited a slow non-chol inergic depolarization which exhibited electrophysiological and pharmacological properties similar to those of substance P-induced depolarization. When ganglion cells were desensitized by continuous application of substance P, preganglionic stimulation failed to induce the slow non-cholinergic depolarization. These results suggest the possibility that the slow non-cholinergic depolarization may be due to the synaptic release of substance P. © 1979.