DIFFERENT EFFECTS OF ACUTE AND CHRONIC IMMOBILIZATION STRESS ON PLASMA TESTOSTERONE LEVELS IN MALE SYRIAN-HAMSTERS

Time-course variations in plasma testosterone levels after various per iods of immobilization stress (10 min, 30 min, 2 h, 6 h) were examined in male Syrian hamsters. The immobilization stress consisted of placi ng the animals in a prone position and wrapping them with flexible ste el wire gauze. This was done at room temperature. Testosterone levels were determined in blood samples taken after the hamsters were decapit ated. Chronic (2 h, 6 h) immobilization stress produced a drastic and enduring fall in plasma testosterone levels. Reduction of plasma testo sterone following the 6-h immobilization stress was observed even 18 h after the stress had been relieved. However, acute (10 min, 30 min) i mmobilization stress did not influence plasma testosterone. These find ings indicated that the effect of immobilization stress on plasma test osterone in hamsters was not biphasic, which it is in rats. Further, t hese results suggest that immobilization stress in hamsters would be a valuable technique with which to investigate the effects of physiolog ical ranges of testosterone on physiological and psychological functio ns.