NADPH-DIAPHORASE AND GNRH - ANATOMICAL RELATIONSHIP IN THE RAT HYPOTHALAMUS

In order to check possible neuroendocrine functions of nitric oxide, c oexistence of gonadotropin-releasing hormone (GnRH) immunoreactivity a nd NADPH-diaphorase (ND) activity was studied in the rat hypothalamus using combined immunocytochemical and histochemical techniques. No coe xistence was found in any hypothalamic nuclei. However, in specific ar eas such as the organum vasculosum of the lamina terminalis, the media l preoptic nucleus, and the periventricular area of the third ventricl e GnRH-immunoreactive and ND-active elements were observed in close an atomical relationship. On the basis of the topographical distribution and morphological characteristics of labelled elements, it is possible to conclude that in normal male animals both markers are expressed in different cells and fibres, but, based in its close proximity, the re leased nitric oxide may be effective in influencing GnRH elements.