Coupling effect of locomotor activity on the rat’s circadian system

Coupling effect of locomotor activity on the rat’s circadian system. Am. J. Physiol. 275 (Regulatory Integrative Comp. Physiol. 44): R580–R587, 1998.—Exercise is recognized to affect circadian rhythmicity in a variety of ways. It masks the expression of other behavioral and physiological rhythms, entrains the master pacemaker, and influences the free-running period of other rhythms. In this paper we study the influence of exercise on the organization of the timing system by analyzing the effect of voluntary locomotor activity on the circadian feeding behavior of rats subjected to different lighting conditions. The availability of wheel running pre-vented loss of feeding circadian rhythmicity under constant bright light (LL) but did not elicit any circadian pattern in rats showing a previous arrhythmic pattern. Under dim red light (DR), the rhythm was more pronounced in exercisin