Food and Water Restriction Shifts Corticosterone, Temperature, Activity and Brain Amine Periodicity

The circadian periodicity of plasma corticosteroid levels was determined in individual adult male and female rats, sampled every 4 hr over a 48-hr period. Access of these rats to food and water was then restricted to 9:30 AM–11:30 AM for a 15-day period, the animals being kept under normal laboratory lighting conditions (lights on 8:00 AM, off 8:00 PM). At the end of this period, such animals had a 12-hr shift in the time of the circadian peak of plasma corticosteroid levels. A similar alteration in the time of the peak of body temperature levels was also seen in these animals. Alteration of patterns of running activity, with a marked increase in daytime running activity was also present in such food and water restricted animals. There was also a reversal of AM/PM ratios of hippocampal norepinephrine and of serotonin levels in these animals. These findings demonstrate that presence of normal light-dark alteration is not sufficient for the maintenance of normal circadian periodicity of plasma corticos-teroid levels. It is suggested that disruption of the sleep-wake pattern induced by food restriction may be a factor responsible for the observed changes. (Endocrinology95: 1195, 1974)