REPRODUCTION IN THE MEXICAN LEAF FROG, PACHYMEDUSA DACNICOLOR .6. PRESENCE AND DISTRIBUTION OF MULTIPLE GNRH FORMS IN THE BRAIN

The presence and distribution of gonadotropin-releasing hormone (GnRH) has been investigated in the Mexican leaf frog, Pachymedusa dacnicolo r, brain during development and in the adult. The ontogenetic pattern of GnRH neurons illustrates their extracranial as well as intracranial sites. Immunohistochemical analysis indicates that GnRH-immunoreactiv e neurons appear during the metamorphic climax. They are located in th e mesencephalon and subsequently other GnRH neurons appear in the peri pheral terminal nerve and anterior preoptic area of the brain. Use of specific antisera and homologous combined with heterologous preabsorpt ion tests indicate that mammalian and chicken GnRH-II-like peptide-con taining neurons are differentially located within the brain, the forme r in the anterior preoptic area and peripheral terminal nerve and the latter in the mesencephalon. HPLC and RIA data suggest the presence of three forms of immunoreactive GnRH in the P. dacnicolor brain. A mamm alian GnRH-like molecule and a chicken GnRH-II-like molecule are prese nt. A third form, suspected to be [hydroxyproline(9)]mGnRH elutes befo re the mammalian GnRH. (C) 1996 Academic Press, Inc.