title: Characterization of appetite-regulating factors in platyfish, Xiphophorus maculatus (Cyprinodontiformes Poeciliidae).
abstract: The regulation of energy in fish, like most vertebrates, is a complex process that involves a number of brain and peripheral hormones. These signals include anorexigenic (e.g. cholecystokinin (CCK) and cocaine- and amphetamine-regulated transcript (CART)) as well as orexigenic (e.g. orexin and neuropeptide Y (NPY)) peptides. Platyfish, Xiphophorus maculatus, are freshwater viviparous fish for which little is known about the endocrine mechanisms regulating feeding. In order to elucidate the role of these peptides in the regulation of feeding of platyfish, we examined the effects of peripheral injections of CCK and orexin on feeding behavior and food intake. Injections of CCK decreased both food intake and searching behavior, while injections of orexin increased searching behavior but did not affect food consumption. In order to better characterize these peptides, we examined their mRNA tissue distribution and assessed the effects of a 10-day fast on their brain and intestine expressions in both males and females. CCK, CART, NPY and orexin all show widespread distributions in brain and several peripheral tissues, including intestine and gonads. Fasting induced decreases in both CCK and CART and an increase in orexin mRNA expressions in the brain and a decrease in CCK expression in the intestine, but did not affect either expressions of NPY. There were no significant sex-specific differences in either the behavioral responses to injections or the expression responses to fasting. The widespread distribution and the fasting-induced changes in expression of these peptides suggest that they might have several physiological roles in platyfish, including the regulation of feeding.
authors.affiliation: Department of Biology, Memorial University of Newfoundland, St. John's, NL A1B 3X9, Canada.
authors.forename: Paul M
authors.initials: PM
authors.lastname: Pitts
authors.affiliation: Department of Biology, Memorial University of Newfoundland, St. John's, NL A1B 3X9, Canada; Department of Biochemistry, Memorial University of Newfoundland, St. John's, NL A1B 3X9, Canada. Electronic address: hvolkoff@mun.ca.
authors.forename: Hélène
authors.initials: H
authors.lastname: Volkoff
mesh_terms: D000818:Animals; D001066:Appetite / Q000187:drug effects / Q000235:genetics*; D002766:Cholecystokinin / Q000008:administration & dosage / Q000378:metabolism; D003532:Cyprinodontiformes / Q000502:physiology; D004435:Eating / Q000187:drug effects / Q000235:genetics; D004734:Energy Metabolism / Q000187:drug effects / Q000235:genetics*; D005215:Fasting; D005247:Feeding Behavior / Q000187:drug effects / Q000502:physiology*; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D008297:Male; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D009478:Neuropeptide Y / Q000235:genetics* / Q000378:metabolism; D000068797:Orexins / Q000008:administration & dosage / Q000378:metabolism; D012333:RNA, Messenger; D000098882:Cocaine- and Amphetamine-Regulated Transcript Protein
chemical_list: D009419:Nerve Tissue Proteins; D009478:Neuropeptide Y; D000068797:Orexins; D012333:RNA, Messenger; D000098882:Cocaine- and Amphetamine-Regulated Transcript Protein; D002766:Cholecystokinin
keywords: Fasting; Food intake; Peptides; Platyfish; mRNA expression