Immunocytochemical and ultrastructural evidence for supra- and subesophageal localization of the dorsal-body cells of the snail Helix aspersa.

Dorsal-body endocrine cells (DBEC) of the snail were studied by means of immunocytochemical and electron microscopic methods at different times of the reproductive cycle. They specifically bind the anti-methionine-enkephalin (vertebrate--opioid-pentapeptide) antibody and are located not only near the cerebral ganglia but also in the connective tissue surrounding the subesophageal ganglia. Ultrastructural characteristics of these subesophageal cells, however, confirm their clear identity with the previously described supraesophageal cells. The quantitative variations of their immunoreactive content allow us to postulate a likely involvement in reproductive physiology (mating and egg laying). These observations prove that the distribution of the classical "dorsal-body cells" is more extensive than has been admitted until now and that they synthesize methionine-enkephalin-like substance(s).