WHEEL RUNNING RAISES BODY-TEMPERATURE AND CHANGES THE DAILY CYCLE IN GOLDEN-HAMSTERS

The purpose of this study was to characterize the influence of wheel-r unning activity on temperature circadian rhythm in golden hamsters. Am plitude of body temperature rhythm was significantly higher in animals that had access to the running wheel. Qualitatively, wheel running re sulted in squaring of temperature rhythm waveform, a phenomenon that w as independent of ambient illumination. When the hamsters had access t o an immobilized wheel, the effect on temperature was no longer observ ed. Fast Fourier Transformation after subtracting 24-h sine waveforms (to rule out harmonics of the principal frequency), indicated distinct secondary components of the rhythms, i.e., a 12-h component in animal s that had access to the wheels and an 8-h component in animals that d id not. The rise in body temperature could be dissociated from the sta rt of the activity period, body temperature augmenting before the time of light-dark transition, while activity increased about 12 min later . On the first night after presentation of an estrous female, the temp erature cycle in male hamsters that did not access to the wheels was s imilar to that found in animals running on the wheels; the effect was no longer observed in subsequent nights. The results contribute to the view that the spontaneous locomotor activity in hamsters has a signif icant effect on temperature cycle.