IMMUNOHISTOCHEMICAL LOCALIZATION OF NEUROPEPTIDE-Y POSITIVE CELL-BODIES AND FIBERS IN FOREBRAIN AND PITUITARY OF THE AFRICAN CATFISH, CLARIAS-GARIEPINUS

The present study reveals the topographic distribution of NPY-immunore active perikarya and fibres in the forebrain of the African catfish, C larias gariepinus, at the light microscopic level. Our interest was ma inly focussed on the possible participation of NPY in the hypothalamo- hypophyseal axis. Different procedures were tested, i.e. on immersion- fixed and paraffin-embedded brains as well as after perfusion-fixation and cryosectioning of the frozen brains. Possible cross-reactivity be tween the NPY-antiserum and FMRF amide was tested and could be exclude d. NPY-immunoreactive perikarya were concentrated in a distinct area o f the telencephalon, i.e. the nucleus entopeduncularis (NE). Especiall y the frontal and lateral parts of the telecephalon were richly innerv ated by NPY-ir fibres. A second distinct concentration of NPY-ir fibre s was found in the area ventralis pars medialis of the telecephalon, k nown to contain GnRH-ir perikarya. The nucleus praeopticus posterioris (NPP) was densely innervated by NPY-positive fibres. The pituitary ha rdly showed innervation by NPY-positive fibres, which were then restri cted to the neurointermediate lobe. The proximal pars distalis (PPD), containing the gonadotropic (GTH) cells, was devoid of NPY-ir fibres. The results of this immunohistochemical study indicate the possibility of an indirect regulation of the GTH-cells by NPY at the level of the brain, rather than a direct regulation via innervation by NPY fibres.