Splitting of the circadian rhythm of body temperature in the golden hamster.

The circadian rhythm of hamster locomotor activity "splits" into two distinct circadian components during conditions of constant illumination. To determine if the circadian rhythm of body temperature also splits under these conditions, body temperature and locomotor activity were monitored concurrently in animals housed in constant illumination. Splitting of the body temperature rhythm into two circadian components was observed in animals manifesting split activity rhythms. Concurrent splitting of both rhythms suggests a common mechanism either for the generation or coupling of these rhythms.