Immunohistochemical localization of PACAP in the ovine digestive system

The localization of immunoreactive PACAP (PACAP-IR) in the entire length of the sheep gastrointestinal tract and the pancreas was studied by an immunohistochemical method. PACAP-IR-containing nerve fibers innervated the longitudinal smooth muscle layer of the mucosa in the esophagus, stomach, and small and large intestines, the muscular layer of the stomach and intestine, Brunner's gland of the duodenum, and the walls of small arteries. PACAP-IR fibers also innervated the exocrine acini, islets of Langerhans, and the small arteries in the connective tissue septa of the pancreas. These findings suggest a regulatory role of PACAP in the digestive system.