ANTICIPATION OF 24-HR FEEDING SCHEDULES IN RATS WITH LESIONS OF THE SUPRACHIASMATIC NUCLEUS

Anticipatory wheel running in response to resticted feeding schedules was studied in rats with lesions of the suprachiasmatic nucleus (SCN) and in sham-operated controls. Despite the absence of circadian periodicity in free-feeding conditions, rats with SCN lesions anticipated restricted access to food at 24-hr intervals in the presence of a light-dark cycle and in constant light. Neither rats with SCN lesions nor controls were able to anticipate feedings at 18-hr intervals. Adrenalectomy did not prevent anticipatory activity to a 24-hr feeding schedule in either group. These results suggest that circadian oscillators outside SCN can be entrained by restricted feeding schedules or, alternatively, that anticipatory activity is based on the hourglass principle, i.e., a clock which requires daily resetting. © 1979 Academic Press, Inc.