IMMUNOHISTOCHEMICAL LOCALIZATION OF GNRH IN THE CRESTED NEWT (TRITURUS-CARNIFEX) BRAIN AND TERMINAL NERVE - A DEVELOPMENTAL-STUDY

Localization of GnRH-immunoreactive neuronal system was studied by imm unohistochemistry in the nasal-brain area of the crested newt, Trituru s camifex. Besides adults, developmental stages were those from hatchl ings up to complete metamorphosis. Neurons containing immunoreactive G nRH were first detected in the nasal area of larvae with yet undiffere ntiated gonads. Subsequently, in prometamorphic stages, GnRH-immunorea ctive cell bodies and fibers were detected in the proximal part of the terminal nerve as well as along the ventromedial surface of the olfac tory bulbs. In older larvae with sexually differentiated gonads and up to the metamorphic climax GnRH-neurons were detected, as a rostral to caudal continuum, along the ventromedial surface of the olfactory bul bs and midtelencephalon. This is exactly the route followed by the ter minal nerve. In the adult brain, besides the presence of occasional Gn RH-neurons and fibers in the terminal nerve proximal to olfactory bulb s, olfactory bulbs and the mid-basal telencephalon, another aggregate of immunoreactive neurons was present in the anterior preoptic area, a nd a greater number of fibers in the habenular area as well as in the infundibular floor, median eminence and pars nervosa. These data sugge st the nasal area to forebrain migration (along the course of the term inal nerve) of GnRH-neurons during development in the crested newt.