Visceral afferent pathways relaying synaptically in the caudal mesenteric sympathetic ganglion

Abstract

The caudal mesenteric sympathetic ganglion of cats was isolated and perfused, and responses of the preganglionic trunks of the ganglion to electrical stimulation of the central end of the hypogastric nerve were studied. Stimulation of the nerve with single square pulses gives rise to early and late responses. Early responses appear after various latent periods and are the result of excitation of transit fibers of groups A, B, and C, whereas the appearance of late responses is associated with the synaptic transmission of excitation in the sympathetic ganglion from afferent sympathetic neurons at the first level (from the pelvic organs to the caudal ganglion) to afferent sympathetic neurons of the second level (from the caudal ganglion and above). Early responses are not blocked, but late responses are blocked by perfusion of the ganglion with azamethonium bromide and magnesium salts, and also by tetanization of the hypogastric nerve at 10–50 Hz. Other facts indicating the synaptic relaying of visceral sympatho-sympathetic afferent pathways in the ganglion are also described.