THE GONADOTROPIN-RELEASING-HORMONE (GNRH) NEURON SYSTEM OF THE CLAWEDTOAD XENOPUS-LAEVIS

The GnRH immunoreactive (GnRH-ir) neuronal system of the Clawed toad X enopus laevis was studied and compared with the GnRH-ir system of the frog Rana esculenta. Polyclonal antibodies against mammalian (mGnRH) a nd chicken type-II GnRH (cGnRH-II), and monoclonal antibodies against mGnRH were used in the study. In the Xenopus laevis, most of the immun opositive neuronal cell bodies were located in telencephalic (35-50 pe r cent) and diencephalic areas (50-65 per cent). About 15-20 per cent of the GnRH perikarya appeared in mesencephalic tegmental regions. Bes ides the larger GnRH fiber tracts present also in mammals, the toad ha s rich mGnRH immunopositive axon population in the mesencephalon and i n the upper part of the medulla. A similar distribution of the GnRH-ir neuronal elements exists in Rana esculenta, but the number of stained cells and fibers was less. Specificity of the staining of cGnRH-IIir structures located in the lower brainstem could not be proved and ther efore the study is only restricted to the findings with mGnRH-antibodi es.