VASOPRESSIN DEFICIENCY AND CIRCADIAN-RHYTHMS DURING FOOD-RESTRICTION STRESS

Vasopressin-containing, Long-Evans (LE) rats and vasopressin-deficient , Brattleboro (DI) rats were monitored for activity and core body temp erature via telemetry. Rats were exposed to a 12-12 light-dark cycle a nd allowed to habituate with ad lib access to food and water. The habi tuation period was followed by an experimental period of 23 h of food- restriction stress in which a 1-h feeding period was provided during t he light cycle. Although both strains of animals showed nocturnal acti vity and temperature rhythms during the habituation period, DI rats we re more active than LE rats. The DI rats also had a lower body tempera ture in the dark. During the experimental period, both strains exhibit ed a phase shift of activity and body temperature correlating with the presentation of food. The DI rats developed a diurnal shift more rapi dly than LE rats. The DI animals showed a dramatic increase in activit y during the light phase and a marked decrease in body temperature dur ing the dark phase. The LE animals showed a significant attenuation of activity, but maintained both nocturnal and diurnal temperature peaks throughout the food-restricted condition.