ENTRAINMENT OF CIRCADIAN-RHYTHMS OF CHOLESTEROL-LDL, CORTICOSTERONE AND MOTOR-ACTIVITY BY FEEDING SCHEDULES IN RATS

The daily variations of locomotor activity, plasma and adrenal cortico sterone levels and cholesterol-LDL were studied in male Wistar rats wi th food ad libitum and feeding restricted to the first 4 hours of the light phase in LD 12:12.Under LD 12:12 (light on from 9:00 to 21:00h) rats with food ad libitum were eating and moving during the dark perio d and the locomotor activity clearly showed a biphasic pattern with th ree harmonic components. Plasma and adrenal corticosterone levels incr eased during the light period and reached a maximum value just before the dark period whereas the acrophase of cholesterol-LDL is found at t he beginning of the light phase. The acrophases of activity, plasma an d adrenal corticosterone levels in the restricted feeding schedule rat s occurred in the first three hours of lighting and the cholesterol-LD L acrophase at the beginning of the dark phase. These results confirm a previous report that the shift of feeding to the light phase seems t o cause a concomitant phase-shift in all the variables measured.