The role of neuropeptides in the sacral autonomic reflex pathways of the cat

Immunohistochemical and pharmacological studies were conducted to examine the origin and function of peptidergic nerves in the sacral autonomic system of the cat. Leucine-enkephalin (L-Enk) immunoreactivity was identified in nerve terminals in peripheral ganglia on the surface of the urinary bladder and in the parasympathetic nucleus in the sacral spinal cord. In colchicine-treated animals L-Enk was also detected in sacral preganglionic neurons (sPGN) identified by retrograde transport of a fluorescent dye. L-Enk terminals in bladder ganglia are believed to arise from sPGN since the terminals were eliminated by transection of the sacral ventral roots. Pharmacological studies indicated that exogenous as well as endogenously released enkephalins have an inhibitory action at both ganglionic and spinal sites in the sacral outflow to the urinary bladder. Peptides were also associated with afferents nerves in the sacral autonomic system. The distribution of substance P, VIP and cholecystokinin in the sacral dorsal horn paralleled the distribution of visceral afferent projections as demonstrated with HRP techniques. Dye labeling combined with immunohistochemistry revealed that some dorsal root ganglion cells projecting to the pelvic viscera contain substance P or VIP.