Precocious puberty in chicks (Gallus domesticus) induced by central injections of neuropeptide Y.

The objective of the study was to determine the role of neuropeptide Y (NPY) and biogenic amines on the onset of puberty in birds. Male broiler chicks were administered chronic intracerebroventricular (ICV) injections of 5 micrograms NPY which produced sexually precocious chicks, determined by advanced secondary sex characteristics. One or two weeks following the beginning of a series of NPY injections, the preoptic area (POA), bed nucleus of the pallial commissure (nCPa), paraventricular nucleus (PVN), and median eminence (ME) were analyzed for biogenic amines. Levels of L-dopa, the precursor of dopamine (DA) were increased within the ME of chicks that responded to treatments by showing advanced sexual maturation when an amino acid decarboxylase blocker was administered prior to sacrifice. The PVN of respondents showed several changes in biogenic amines, while the nCPa displayed a biogenic amine metabolite of unknown identity which was significantly lower in respondent chicks. In contrast to mammals, L-dopa was detectable within the nCPa, PVN, and ME regardless of whether an enzymatic blocker of amino acid decarboxylase was administered to chicks prior to sacrifice. Results suggest that increased brain levels of NPY and DA, the latter specifically occurring within the ME, are associated with the onset of puberty. Due to the several significant differences found in biogenic amino levels within the PVN of respondent chicks, this nucleus, similar to the ME may be a highly active and integrative neural structure during the onset of puberty in chicks.