Effect of sulfamethazine on sexual precocity and neuropeptide Y neurons within the tuberoinfundibular region of the chick brain.
Neuropeptide Y (NPY) has been implicated in the sexual maturation process in chicks and other species. This study attempted to identify specific neural sites where NPY could influence gonadotrophin-releasing hormone (GnRH) neurons during maturation as evidenced by immunocytological changes. To do this sulfamethazine (SMZ), an antibiotic known to advance sexual maturation in male chicks, was used to elicit early testes development. One week posthatch, 20 chicks were fed either a control ration or one with 0.2% SMZ for 2 weeks or 5 weeks. At 3 and 6 weeks of age, birds were perfused through the heart, brains removed, and prepared for immunocytochemical assay for either NPY or GnRH. Results showed that chicks given SMZ had significantly greater testes weight compared to controls at both ages (p < or = 0.05) while body weight did not differ significantly between these groups at either age. The results of cell quantification showed no difference in the number of GnRH neurons between the SMZ chicks and controls in either the bed nucleus of the pallial commissure or the anterior lateral thalamic nucleus (LA) at 3 or 6 weeks of age. There was a significantly greater number of GnRH neurons found within the LA of 6-week compared to 3-week-old control chicks. A ratio of the mean width of the external zone (EZ) of median eminence (ME) to the total width of ME showed no significant difference between the experimental and control animals at either 3 or 6 weeks of age. The ratio EZ/ME did, however, increase as a function of age. The results of the assay for immunoreactivity to NPY showed no significant difference in the number of NPY neurons found within the nucleus marginalis tractus opticus between treatment groups at either age. A highly significant increase in NPY neurons was found within the infundibular nucleus (IN) and the internal zone of the ME of SMZ-treated chicks compared to controls at 3 weeks of age. Data suggest that NPY-like neurons within the IN complex may serve an important role regarding the early stages of sexual maturation in chicks.
Walsh
K M
KM
Department of Animal and Avian Sciences, University of Maryland, College Park 20742, USA.
Kuenzel
W J
WJ
D000818:Animals; D000890:Anti-Infective Agents / Q000494:pharmacology*; D001921:Brain / Q000166:cytology / Q000187:drug effects / Q000254:growth & development*; D002645:Chickens / Q000254:growth & development*; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism; D007150:Immunohistochemistry; D008297:Male; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D009478:Neuropeptide Y / Q000378:metabolism*; D012741:Sexual Maturation / Q000187:drug effects*; D013418:Sulfamethazine / Q000494:pharmacology*
D000890:Anti-Infective Agents; D009478:Neuropeptide Y; D007987:Gonadotropin-Releasing Hormone; D013418:Sulfamethazine