LOCALIZATION OF REGULATORY PEPTIDES IN THE GASTROINTESTINAL TRACT OF THE STRIPED DOLPHIN, STENELLA COERULEOALBA (MAMMALIA, CETACEA) - AN IMMUNOHISTOCHEMICAL STUDY

摘要

Samples of oesophagus, first, second and third stomach, duodenal ampulla, proximal intestine and distal intestine including rectum were obtained from striped dolphins (Stenella coeruleoalba) stranded along Italian coasts, fixed in formalin and used for immunohistochemistry. The possible presence of neuropeptides and the biogenic amine serotonin was investigated by a labelled streptavidin-biotin method. Neuropeptide Y (NPY)-, substance P-, calcitonin gene-related peptide (CGRP)-, metenkephalin-, gastrin releasing peptide (GRP)/ bombesin-, and somatostatin-like immunoreactivities were present in the submucosal as well as the myenteric plexuses, even with differences of distribution in the various organs. Vasoactive intestinal poly-peptide (VIP)-like immunoreactivity was detected in the submucosal plexus, whereas beta-endorphin- and leu-enkephalin-like immunoreactivities were shown in the myenteric plexus only. NPY-, substance P-, CGRP-and VIP-like-immunoreactivities were also observed in perivascular nerve fibres. In addition, VIP-, GRP- and somatostatinlike immunoreactivities were detected in myelinated nervous bundles. These were localized in the submucosal and muscular layers all along the gastrointestinal tract, and possibly sustain an exceptionally rapid response of the target structures. It is noteworthy that peptidergic axons in the wall of the gut of the majority of mammals are unmyelinated. A somatostatin-like peptide was identified in epithelial cells only in the second stomach, whereas in terrestrial mammals this endocrine cell type occurs widely. Immunoreactivity to serotonin was never detected, and this is a further difference in comparison with the majority of other mammals. [References: 86]