Immunohistochemical studies on the intrinsic pancreatic nerves in the chicken

A peroxidase anti-peroxidase method or an avidin-biotinylated complex method was used to visualize neural elements immunostained for several neuropeptides in the chicken pancreas. Pancreatic ganglion cells were only immunoreactive with vasoactive intestinal polypeptide (VIP), galanin and substance P (SP) antisera. VIP-immunoreactive (IR) ganglion cells were the most numerous, and most of them also showed the distinct immunoreaction with galanin. VIP- and galanin-IR nerve fibers were observed in the exocrine portion, the adventitia of the artery and the connective tissue of the ductal wall. The number and distribution of the VIP- and galanin-IR nerve fibers around the artery and duct were similar. SP-IR nerve fibers were found mainly close to the blood vessel. SP- and CGRP-IR nerve fibers were detected in the VIP-IR ganglion and extrapancreatic nerve bundle. Tyrosine hydroxylase (TH)- and aromatic L-amino acid decarboxylase (AADC)-IR nerve fibers were observed as nerve bundles in the interlobular space or extrapancreatic nerves. Consequently, VIP and galanin coexist in the intrinsic neural elements. SP is partially located in the intrinsic neural elements, but most of it seems likely to originate from the extrinsic ganglion. It is probable that calcitonin gene related peptide (CGRP)-, TH- and AADC-IR nerve fibers have an extrinsic origin.