NEUROPEPTIDE-Y - LOCALIZATION IN THE BRAIN AND PITUITARY OF THE DEVELOPING FROG (RANA-ESCULENTA)

The immunohistochemical localization of neuropeptide Y (NPY)-like pept ide has been investigated in the peripheral terminal nerve, brain and pituitary of the frog, Rana esculenta, during development. Soon after hatching, a rather simple NPY-immunoreactive (-ir) neuronal system is present, with elements located mainly in the diencephalon. When hind l imbs appear and develop, the NPY-neuronal system undergoes considerabl e elaboration and NPY-ir perikarya appear in several regions of the te lencephalon (dorsal, medial, and lateral pallium; medial septum; medio ventral telencephalon; anterior preoptic area), diencephalon (ventrome dial, central and posterior thalamic nuclei; suprachiasmatic nucleus; infundibulum), mesencephalon (anteroventral mesencephalic tegmentum), and rhombencephalon (central grey; area of the cerebellar and vestibul ar nuclei). The frequency of NPY-ir neurons increases during larval de velopment, and then decreases in the anterior preoptic area during the metamorphic climax. Dense plexuses of NPY-ir fibers are formed in sev eral brain areas. NPY-ir fibers are found in the peripheral terminal n erve, and ir-neurons through its course along the ventromedial surface of the olfactory bulbs. NPY-ir fiber projections to the median eminen ce and pars intermedia derive mainly from the ventral infundibular gro up of NPY-ir neurons, with a contribution from the suprachiasmatic gro up of NPY neurons. NPY and carboxyl terminal flanking peptide of prone uropeptide Y coexist in the same neurons throughout the brain. The ont ogenetic pattern of NPY-ir neuronal system in the brain of Rana escule nta is remarkably different than that reported for Xenopus laevis.