[Rhythmic organization of compulsory swimming and its relation to the behavioral characteristics of rats].

Seconds' biorhythms manifesting themselves during protracted swimming were studied in 52 white outbred rats of both sexes. In rats with higher rhythm frequency short immobilization periods dominated in swimming. They had shorter immobilization time. These rats relearned easier the direction of avoidance reaction in Y-maze, were more mobile in the open field, more often washed up, more rarely defecated and urinated. The seconds' rhythms may be used for evaluation of the ability of animals for adaptation to changing behavioural situation.