Occurrence of melanotropin- and corticotropin-like material in the cerebral ganglion of a protochordate.

The cerebral ganglion of the ascidian Styela plicata has been investigated using cytochemical and immunocytochemical methods. Peptidergic neurons are present mainly in the cortical zone and they contain alpha-MSH or ACTH-like immunoreactive substances. Coexistence of the two pituitary hormones is also demonstrated in some neurons by means of the double immunofluorescence method. The possible physiological role of these peptides in the ascidian central nervous system is discussed as well as the conservative characteristics of alpha-MSH- and ACTH-like molecules.