Effect of Melatonin on the Processes of Exotrophy in Common Carp Cyprinus carpio

Abstract

The effect of melatonin on the initial (feeding) and central link (digestion) of exotrophy in juvenile common carp Cyprinus carpio was investigated in parallel for the first time. The effect of intraperitoneal injections of the hormone at a concentration of 100 and 200 ng/g of body weight on locomotor activity and food consumption, as well as on the activity of digestive enzymes in the intestinal mucosa and chyme, was studied. It was shown that five hours after the administration of the hormone, food consumption and the activity of digestive enzymes in the intestinal mucosa decrease, while the locomotor activity of fish and the enzymatic activity of the chyme do not change significantly. Food consumption is significantly (by factor of 2.2) reduced as a result of the administration of the hormone at a dose of 200 ng/g body weight. The level of caseinolytic and hemoglobinolytic activity of peptidases and amylolytic activity of the intestinal mucosa at this dose also decrease significantly: by 27, 54 and 42%, respectively, compared to the control. The injection of melatonin at a dose of 100 ng/g causes a slight decrease in the level of enzymatic activity of the intestinal mucosa. The mechanisms of the effect of melatonin on the processes of exotrophy in fish are discussed.