Localization of neuropeptide Y mRNA and peptide in the chicken hypothalamus and their alterations after food deprivation, dehydration, and castration

Localization of neuropeptide Y (NPY) mRNA in the hypothalamus of chickens w as studied by in situ hybridization with digoxigenin-labeled chicken NPY cR NA probe. The largest number of perikarya-expressing NPY mRNA was found wit hin the mediobasal hypothalamus, including the infundibular nucleus, inferi or hypothalamic nucleus, and median eminence. Many NPY perikarya were noted to surround the nucleus rotundus and to be present in the supraoptic nucle us. Moreover, some perikarya were detected in the nucleus of basal optic ro ot, bed nucleus pallial commissure, and nucleus striae terminalis close to the lateral forebrain bundle. NPY-immunoreactive nerve fibers were densely distributed in these regions containing the NPY mRNA-expressing perikarya. Following food deprivation for four days, perikarya-expressing NPY mRNA and peptide were markedly increased in the mediobasal hypothalamus and particu larly so in the infundibular nucleus. No changes, however, were detected in other regions containing NPY-positive perikarya. Water deprivation induced less increase in NPY-positive perikarya in the mediobasal hypothalamus com pared to food deprivation. After gonadectomy, the number of NPY-positive pe rikarya in the mediobasal hypothalamus was unaltered. Northern blot analysi s with P-32-labeled chicken NPY cDNA probe demonstrated that a 2.7-fold inc rease of NPY mRNA was induced by starvation and a 1.5-fold increase was ind uced by dehydration, whereas the NPY mRNA band remained unchanged after gon adectomy. Thus, it seems that NPY neurons located in the mediobasal hypotha lamus are involved in feeding behavior but not reproductive activity. (C) 2 001 Wiley-Liss, Inc.