Characterization of appetite-­‐regulating factors in platyfish, Xiphophorus maculatus (Cyprinodontiformes Poeciliidae) and cunner, Tautogolabrus adspersus

• Main Author: Pitts, Paul
• Format: Thesis
• Language: English
• Published: Memorial University of Newfoundland 2016
• Subjects: Newfoundland; North Atlantic
• Online Access: https://research.library.mun.ca/12874/; https://research.library.mun.ca/12874/1/thesis.pdf

The regulation of energy in fish, like most vertebrates, is a complex process that involves a number of chemical signals originating and networking in different parts of the brain and throughout the body. These signals include anorexigenic hormones that suppress feeding and hunger [e.g. cholecystokinin (CCK) and cocaine-­‐and amphetamine-­‐regulated transcript (CART)] as well as orexigenic peptides that stimulate feeding behaviour and food intake [e.g. orexin and neuropeptide Y (NPY)]. Platyfish, Xiphophorus maculatus, are freshwater viviparous fish found in tropical waters from South America to northern Mexico. Although these fish have been the object of numerous physiology and behavioural studies, very little is known about the endocrine mechanisms regulating their feeding. In order to elucidate the role of these peptides in the regulation of feeding, we examined the effects of peripheral injections of CCK and orexin on feeding behaviour and food intake. Injections of CCK decreased both food intake and searching behaviour, while injections of orexin increased searching behaviour but did not seem to have an effect on food consumption. In order to better characterize these peptides, we performed tissue distribution and gene expression studies. Tissue distribution studies show that CCK, CART, NPY and orexin all show a widespread distribution in brain and several peripheral tissues, including intestine. In addition, we compared the expression of these peptides in brain and gut between fed and 10-­‐day fasted platyfish using qPCR. Fasting caused decreases in both CCK and CART mRNA expressions in the brain and a decrease in CCK expression in the intestine. There was also a significant increase in orexin mRNA expression in the brain as a result of fasting. Cunners, Tautogolabrus adspersus, are cold-­‐water oviparous (egg laying) marine fish that can be found from Northern Newfoundland to all along the coast of the western North Atlantic. In cunner, fasting for 10 days caused a decrease in CCK in the brain, and a ...