Isolation of cDNAs and gene expression of three feeding-related neuropeptides, neuropeptide Y (NPY), cocaine and amphetamine regulated transcript (CART) and orexin, in Atlantic cod (Gadusmorhua)

Kehoe, Amy (2005) Isolation of cDNAs and gene expression of three feeding-related neuropeptides, neuropeptide Y (NPY), cocaine and amphetamine regulated transcript (CART) and orexin, in Atlantic cod (Gadusmorhua). Masters thesis, Memorial University of Newfoundland.

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Abstract

Our understanding of the regulation of food intake in fish has evolved from experiments in the 1970's that identified feeding centres of the fish brain, to recent ones where the molecular cloning of central and peripheral factors regulating appetite is performed. In fish, food intake is regulated by the hypothalamus where neuropeptides controlling feeding are produced. Many neuropeptides have been implicated in the regulation of food intake in fish. In this study, we identified complete cDNAs encoding Neuropeptide Y (NPY) and Cocaine and amphetamine regulated transcript (CART) and a 348 bp partial cDNA of orexin from Atlantic cod (Gadus morhua) brain. There is a high degree of identity between the predicted amino acids of Atlantic cod NPY and CART and vertebrate homologs, and we found, using RT-PCR, that NPY and CART mRNA is localized not only in the brain (including the hypothalamus) but also in peripheral tissues. For example, both NPY and CART mRNA are expressed in the ovary, and NPY mRNA is also expressed in the gut, kidney and heart. We examined NPY and CART mRNA expression during a daily feeding period and following food deprivation. Peri-prandial variations were seen in both NPY and CART expression, and CART was affected by fasting. Finally, we examined the effects of environmental temperature on the control of feeding by examining NPY and CART mRNA expression in fish acclimated to 2°C, 5°C, 11°C and 15°C. Our results suggest that both NPY and CART are involved the control of food intake in cod since they are strongly expressed in the hypothalamus, an area of the brain regulating feeding, and they respond to feeding. Further, CART mRNA expression appears to be regulated by temperature whereas NPY does not.

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