Neuropeptide-Y in the trout brain and pituitary : localisation characterization and action on gonadotropin release

Using a specific antiserum raised against synthetic neuropeptide-Y (NPY), the distribution of NPY-like immunoreactivity in the brain and pituitary of the trout Oncorhynchus mykiss has been examined with the indirect immunofluorescence and peroxidase-antiperoxidase methods. The highest density of NPY-immunoreactive elements was found in the basal telencephalon and hypothalamus. In particular, NPY-immunoreactive neurons were located in the nucleus entopeduncularis and the preoptic nucleus. NPY-immunoreactive fibers were observed throughout the trout brain. The preoptic nucleus, the suprachiasmatic nucleus, and the nucleus entopeduncularis were densely innervated. In addition, NPY-positive fibers were detected in the nucleus lateralis tuberis and in the distal and intermediate lobes of the pituitary. The NPY-like peptide of the trout brain was characterized by combining HPLC analysis and radioimmunological detection. Serial dilutions of trout hypothalamus and pituitary extracts produced displacement curves that were parallel to the standard curve. HPLC analysis resolved a major peak which was slightly less hydrophobic than porcine NPY. The possible effect of NPY, either alone or in combination with a GnRH antagonist, on gonadotropin (GtH) release from trout pituitaries was investigated using a perifusion system technique