The occurrence and distribution of GnRH in the brain of Atlantic hagfish, an agnatha, determined by chromatography and immunocytochemistry

Abstract

In Atlantic hagfish (Myxine glutinosa), chromatographic and immunocytochemical evidence showed that the brain contains a gonadotropin-releasing hormone (GnRH)-like molecule that is closely related to lamprey GnRH-III. The chromatographic studies (HPLC) used specific antisera directed against mammalian GnRH and lamprey GnRH-I. In addition to these antisera, other specific antisera were tested in immunocytochemical studies, including chicken GnRH-I, chicken-GnRH-II, salmon GnRH, and lamprey GnRH-III. Using a lamprey GnRH-I antiserum, an early eluting GnRH form coeluted on HPLC with lamprey GnRH-III standard and an unknown form coeluted with the chicken GnRH-II standard. Radioimmunoassay of brain tissue detected GnRH immunoreactivity only when the lamprey GnRH-I antibody was used. A GnRH-like immunoreactivity was also obtained immunocytochemically in the neurohypophysis with the use of antisera against chicken GnRH-II, salmon GnRH, lamprey GnRH-I, and lamprey GnRH-III. These studies indicate that, contrary to earlier reports, hagfish do have a GnRH-like molecule that is more closely related, in terms of immunological determinants, to lamprey GnRH-III than to other currently known vertebrate GnRH molecules.