Ghrelin, neuropeptide Y (NPY) and cholecystokinin (CCK) in blunt snout bream (Megalobrama amblycephala): cDNA cloning, tissue distribution and mRNA expression changes responding to fasting and refeeding.

Blunt snout bream (Megalobrama amblycephala Yih, 1955) is an endemic freshwater fish in China for which the endocrine mechanism of regulation of feeding has never been examined. Ghrelin, neuropeptide Y (NPY) and cholecystokinin (CCK) play important roles in the regulation of fish feeding. In this study, full-length cDNAs of ghrelin, NPY and CCK were cloned and analyzed from blunt snout bream. Both the ghrelin and NPY genes of blunt snout bream had the same amino acid sequences as grass carp, and CCK also shared considerable similarity with that of grass carp. The three genes were expressed in a wide range of adult tissues, with the highest expression levels of ghrelin in the hindgut, NPY in the hypothalamus and CCK in the pituitary, respectively. Starvation challenge experiments showed that the expression levels of ghrelin and NPY mRNA increased in brain and intestine after starvation, and the expression levels of CCK decreased after starvation. Refeeding could bring the expression levels of the three genes back to the control levels. These results indicated that the feeding behavior of blunt snout bream was regulated by the potential correlative actions of ghrelin, NPY and CCK, which contributed to the defense against starvation. This study will further our understanding of the function of ghrelin, NPY and CCK and the molecular mechanism of feeding regulation in teleosts.