2 MEALS IN THE ACTIVE PERIOD OF THE RAT BOTH ENTRAIN FOOD-ANTICIPATORY ACTIVITY

We examined the effect of presenting two meals at fixed times on the a ctivity of six intact female rat. Rats maintained on a 12-12 h light-d ark cycle were fed; ad lib, at tow randomly chosen times during the ac tive period, and at 3 and 9 h, 1 and 7 h, and 5 and 11 h after light o ffset. During ad lib and random feeding conditions, wheel turning prim arily occurred during the first half of the active period. During fixe d-time feeding conditions, wheel turning was concentrated around the t imes of meal availability. To determine whether anticipatory wheel tur ning during fixed-time feeding conditions was based on a circadian mec hanism, each condition was followed by a test; light cues were omitted and rats were deprived of food for 2 consecutive days. Wheel turning patterns observed while a feeding condition was in effect persisted du ring meal omission. Nest and food/water compartment visits were not as sensitive to feeding times. Meals may have modified bouts of activity that are also synchronized by light-dark cycles.