The effects of peripherally injected serotonin on feeding and locomotor activities in carp Cyprinus carpio L.

Abstract

The influence of intraperitoneal (IP) and intramuscular (IM) injections of serotonin (5-hydroxytryptamine or 5-HT, 10 μg/g body weight) on a number of parameters of feeding behavior and locomotor activity in carp Cyprinus carpio L. has been investigated. It was shown that exogenous serotonin decreased various parameters of feeding and locomotor activities, and IM injections caused stronger inhibitory effect than IP injections. IP administration of this biogenic amine reduced the food intake in fishes of different age groups, induced an increase of the search reaction time (the latency to leave the starting chamber after its front wall was raised, or latency period for feeding of fish) in carp fingerlings in the experiments with “single” feeding. IM injections significantly lowered food intake of carp fingerlings in 1, 5 and 53 h, two other parameters—during all period of observation. In the experiments with “group” feeding food intake, duration of “group” feeding and total duration of feeding decreased during all period of observation after IM administration and in 1 h after IP injections only. Duration of “single” feeding and locomotor activity were changed less distinctly. The strongest effect of serotonin (up to 100%) was shown for duration of “group” feeding. It was supposed that inhibitory effects of exogenous serotonin on feeding and locomotor activities in carps were caused by its peripheral effects as well as by partial involving of central effect.