CORTICOSTERONE BASAL LEVELS AND RESPONSE TO ETHER ANESTHESIA IN RATS ON A WATER-DEPRIVATION REGIMEN

Male hooded rats were subjected to a 23 2 3-hr water deprivation schedule for 8 weeks. The corticosterone levels of these rats increased between 0800 and 1000 hr if they had always been watered at 1200 hr, but increased between 0600 and 0800 if the daily watering time had been randomized between 0800 and 1200 hr the previous 8 weeks. The corticosterone levels remained high until 1200 hr for both treatments. The results indicate temporal entrainment and a stable, elevated baseline corticosterone concentration. Eight weeks on the deprivation schedule resulted in accelerated corticosterone responses to acute stressors, but the acceleration was minimized when the rats were maintained under continuous ether anesthesia. The procedure of blood sampling under ether anesthesia is valid for water-deprived rats if the sample is drawn within 1.5 min, but it is not valid for up to 3 min as in ad lib rats. © 1979.