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

Simple Summary: Cholecystokinin (cck) is an important factor in regulating feed intake. According to a previous study, replacing fish meal (FM) in the diet of largemouth bass could downregulate the expression of the cck gene; however, the underlying regulatory mechanism remains unclear. Therefore, we investigated the effect of cck on feed intake and its potential mechanism of action via injecting exogenous CCK peptide and its receptor antagonist. This study's results indicate that cck could regulate the feed intake of largemouth bass through regulating feeding-related genes in the brain and intestine. Furthermore, cck required binding with the receptor to inhibit feed intake more effectively in largemouth bass, and the binding effect of cholecystokinin receptor 1 (CCK1R) was better than that of cholecystokinin receptor 2 (CCK2R), which could lay a theoretical foundation for the study of fish feeding regulation. This study investigated the role of cholecystokinin (cck) in the feeding regulation of largemouth bass (Micropterus salmoides) via peptide activation and antagonist inhibition. The results show that the cck 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 cck in the brain. Moreover, the activation of cck 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, cck could regulate the feed intake of largemouth bass through regulating feeding-related genes in the brain and intestine. In addition, cck 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. [ABSTRACT FROM AUTHOR]