title: Hypothalamic gonadotropin-inhibitory hormone precursor mRNA is increased during depressed food intake in heat-exposed chicks.
abstract: The regulation of food intake in chickens (Gallus gallus domesticus) represents a complex homeostatic mechanism involving multiple levels of control, and regulation during high ambient temperatures (HT) is poorly understood. In this study, we examined hypothalamic mRNA expression of gonadotropin-inhibitory hormone (GnIH) to understand the effect of HT on an orexigenic neuropeptide. We examined the effects of HT (35 °C ambient temperature for 1, 24 or 48 h) on 14-day old chicks. HT significantly increased rectal temperature and suppressed food intake, and also influenced plasma metabolites. The expression of GnIH precursor mRNA in the diencephalon was significantly increased in chicks at 24-and 48 h of HT when food intake was suppressed significantly, whilst no change was observed for GnIH precursor mRNA and food intake at 1h of HT. In situ hybridization and immunocytochemistry further revealed the cellular localization of chicken GnIH precursor mRNA and its peptide in the paraventricular nucleus (PVN) in the chick hypothalamus. We examined plasma metabolites in chicks exposed to HT for 1 or 48 h and found that triacylglycerol concentration was significantly higher in HT than control chicks at 1h. Total protein, uric acid and calcium were significantly lower in HT chicks than control chicks at 48h. These results indicate that not only a reduction in food intake and alteration in plasma metabolites but also the PVN-specific expression of GnIH, an orexigenic agent, may be induced by HT. The reduced food intake at the same time as GnIH expression was increased during HT suggests that HT-induced GnIH expression may oppose HT-induced feeding suppression, rather than promote it. We suggest that the increased GnIH expression could be a consequence of the reduced food intake, and would not be a direct response to HT.
authors.affiliation: Department of Bioresource Sciences, Faculty of Agriculture, Kyushu University, Fukuoka 812-8581, Japan. vc-sur@agr.kyushu-u.ac.jp
authors.forename: Vishwajit S
authors.initials: VS
authors.lastname: Chowdhury
authors.forename: Shozo
authors.initials: S
authors.lastname: Tomonaga
authors.forename: Shotaro
authors.initials: S
authors.lastname: Nishimura
authors.forename: Shoji
authors.initials: S
authors.lastname: Tabata
authors.forename: John F
authors.initials: JF
authors.lastname: Cockrem
authors.forename: Kazuyoshi
authors.initials: K
authors.lastname: Tsutsui
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Furuse
mesh_terms: D000818:Animals; D030161:Avian Proteins / Q000235:genetics / Q000378:metabolism; D015992:Body Mass Index; D002118:Calcium / Q000097:blood / Q000378:metabolism; D002645:Chickens; D003345:Corticosterone / Q000097:blood / Q000235:genetics / Q000378:metabolism; D004435:Eating / Q000235:genetics*; D006062:Gonadotropins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D006358:Hot Temperature; D007028:Hypothalamic Hormones / Q000235:genetics* / Q000378:metabolism; D008297:Male; D009479:Neuropeptides / Q000235:genetics / Q000378:metabolism; D010286:Paraventricular Hypothalamic Nucleus / Q000378:metabolism / Q000502:physiology*; D012322:RNA Precursors / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D014280:Triglycerides / Q000097:blood / Q000235:genetics / Q000378:metabolism; D014527:Uric Acid / Q000097:blood / Q000378:metabolism
chemical_list: D030161:Avian Proteins; D006062:Gonadotropins; D007028:Hypothalamic Hormones; D009479:Neuropeptides; D012322:RNA Precursors; D012333:RNA, Messenger; D014280:Triglycerides; D014527:Uric Acid; D002118:Calcium; D003345:Corticosterone