Scheduled exercise modulates daily rhythms of behavior, physiology, and gene expression in mice

Light is the primary environmental signal that synchronizes the circadian system coordinating the temporal patterning of behavior and underlying biological processes. Other cues such as activity may be able to influence the output of this system. In our studies, we used scheduled wheel access to manipulate magnitude and phasing of locomotor activity and explored subsequent effects on daily rhythms of heart rate (HR) and body temperature in WT mice. Mice were subject to 5 wheel access conditions: no access, free access, Zeitgeber (ZT) 12–18, ZT 18–24 and ZT 0–6 access. We found that giving the mice the opportunity to run on a wheel can significantly increase activity levels and therefore considered as exercise. Furthermore, shifting the phase of exercise with wheel access altered the temporal patterning of rhythms in HR and body temperature. We also examined the effects of wheel access induced exercise on the molecular clock underlying the generation of circadian rhythms. Using the Per2:LUC knockin mouse, we found that exercise at ZT 0–6 shifted the phase of PER2:LUC expression in the SCN and peripheral tissues. We conclude that wheel access induced exercise can be used to shape daily rhythms of activity in mice and influence the rhythms of other biological outputs such as HR and body temperature. Activity can also influence the phasing of PER2:LUC expression in the SCN and peripheral tissues.