Immunocytochemical identification of some regulatory peptides (gastrin, gastrin-releasing peptide, neurotensin and vasoactive intestinal polypeptide) in the Harderian gland of the green frog, Rana esculenta.

The presence and distribution of gastrin-, gastrin-releasing peptide-, neurotensin- and vasoactive intestinal polypeptide-like immunoreactivity in the Harderian gland of Rana esculenta were studied at different times of the annual cycle. Gastrin-releasing peptide, neurotensin and vasoactive intestinal polypeptide-like substances were found either in the glandular cells, or in the nerve fibers surrounding the glandular acini. Gastrin-like immunoreactivity was confined to the glandular cells. The immunoreactivity varied during the annual cycle, with the greatest concentration being noted during the recovery phase of glandular secretory activity.