Immunohistochemical localization of several neuropeptides in the adrenal gland of five species belonging to the order of Squamata

Abstract

Recent studies have shown that several peptides coexist together with catecholamines within chromaffin cells. It has been demonstrated that the same chromaffln cell contains two or more bioactive substances forming several cellular subpopolations. These peptides play an important physiological role within the adrenal gland. Since very few data were available about the localization of peptides in reptiles, the aim of this study was to investigate the presence of different neuropeptides within the adrenal gland of species belonging to different families of this class of vertebrates. In particular, the immunohistochemical distribution of Leu‐enkephalin (Leu‐ENK), neuropeptide Y (NPY), somatostatin (SOM), substance P (SP), and vasoactive intestinal peptide (VIP) was studied in several species belonging to the order of Squamata. The results obtained showed that some of these peptides, e.g. SP, NPY, and VIP were widely distributed in most chromaffin cells, whereas Leu‐ENK was present only in a small number. Considering the distribution of all neuropeptides, there were no fundamental differences among different species, except for the peculiar localization of SOM in the Tarentola mauritanica adrenal gland. The results obtained represent a morphological basis for further studies about the role played by these peptides in the control of reptilian adrenal gland functionality.