Recovery of anticipatory activity to restricted feeding in rats with ventromedial hypothalamic lesions.

Entrainment of circadian activity rhythms to a fixed daily mealtime was measured in intact and ventromedial hypothalamic (VMH) lesioned rats housed in tilt-cages. Intact rats showed a clear increase in activity for 2-3 hr prior to the 2 hr daytime feeding period. Anticipatory activity in lesioned rats was attenuated or absent during restricted feeding 5-9 weeks after surgery, but was evident in all rats, even those bearing apparently total VMH damage, during a second restricted feeding schedule 14-21 weeks after surgery. These results show recovery of function and argue against a necessary role for the VMH in food entrained rhythms.