Role of Cholecystokinin (cck) in Feeding Regulation of Largemouth Bass (Micropterus salmoides): Peptide Activation and Antagonist Inhibition

This study investigated the role of cholecystokinin (<i>cck</i>) in the feeding regulation of largemouth bass (<i>Micropterus salmoides</i>) via peptide activation and antagonist inhibition. The results show that the <i>cck</i> gene was expressed in various tissues, with the highest expression level occurring in the brain. Feeding, continuous feeding, and refeeding after fasting could significantly improve the mRNA levels of <i>cck</i> in the brain. Moreover, the activation of <i>cck</i> via injecting an exogenous CCK peptide could inhibit feed intake by regulating the mRNA levels of anorexigenic and feed-promoting factors in the brain and intestine. Furthermore, the CCK peptide reduced feed intake; however, the presence of an antagonist (Ly225910-CCK1R and devazepide-CCK2R) could reverse this effect through regulating the mRNA levels of anorexigenic and feed-promoting factors in the brain and intestine. Treatment with devazepide + CCK (CCK2R) reversed feed intake more effectively than Ly225910 + CCK (CCK1R) treatment. In summary, <i>cck</i> could regulate the feed intake of largemouth bass through regulating feeding-related genes in the brain and intestine. In addition, <i>cck</i> required binding with the receptor to inhibit feed intake more effectively in largemouth bass, and the binding effect of CCK1R was better than that of CCK2R.