ALTERATION IN CIRCADIAN-RHYTHM OF PLASMA-CORTICOSTERONE IN RATS FOLLOWING SOCIOPSYCHOLOGICAL STRESS-INDUCED BY COMMUNICATION BOX

The purpose of present study was to investigate the physiological char acteristics of sociopsychological stress induced by the communication box method. In this method, the nonfoot shocked rats were used as the psychological stressed experimental group. The stress exposure was loa ded for 1 h between 0900 and 1000, daily. The changes in circadian rhy thm of plasma corticosterone were studied following the 3-day, 5-day, or 10-day stress exposure, respectively. Plasma corticosterone levels of foot shocked rats and nonfoot shocked rats following the 3-day or 5 -day stress exposure were significantly higher than those of control r ats. Particularly, the marked elevation of plasma corticosterone was o bserved at the peak time of circadian rhythm (2100) in the both stress groups. Consequently, the amplitude of 24 h rhythm increased signific antly, but the acrophase was not changed. However, the changes of plas ma corticosterone levels of both stress groups following the 10-day st ress exposure approached those of control group. These results suggest that the repeated exposure of sociopsychological stress can influence the circadian rhythm of plasma corticosterone. The communication box method may be a valuable tool for researching the etiology of human ps ychiatric disorders with rhythm disturbance.