Vasoactive intestinal polypeptide in visceral afferent pathways to the sacral spinal cord of the cat.

Immunohistochemical studies revealed that vasoactive intestinal polypeptide (VIP) is localized primarily to sacral segments of the cat's spinal cord. VIP is most prominent in afferent axons and terminals in Lissauer's tract and in lateral laminae I and V of the dorsal horn. The distribution of VIP terminals is very similar to that of visceral afferent projections identified by horseradish peroxidase. Dye-tracing experiments combined with immunohistochemistry demonstrated that VIP is located in visceral afferent perikarya in the sacral dorsal root ganglia and also in terminals in the sacral autonomic nucleus. These observations suggest that VIP is a neurotransmitter in afferent projections from the pelvic viscera.