REM-sleep deprivation, stress and emotional behavior in rats.

Eighty-eight adult white rats were divided into 9 groups. Groups 1 and 2 served as controls. The rats of Group 3 were repeatedly aroused during 4 days at the very onset of each REM-sleep period by direct midbrain reticular formation stimulation. This deprivation decreased the daily amount of REM-sleep by 70%, while slow-wave sleep was reduced by 10% only. In Group 4, the animals were given food and water for 1 h a day only. Groups 5 and 6 were subjected to immobilization and cold stress, respectively. Groups 7, 8 and 9 were deprived of REM-sleep on platforms of 15, 11 and 6.5 cm in diameter, respectively. Stress was estimated by the classical Selye's triad: weight of adrenals and thymus and gastric ulceration. Emotionality was measured in the open-field and also by self-stimulation of the lateral hypothalamus. Neither emotional behavior disturbances nor Selye's stress features were found after REM-deprivation in Group 3. Moreover, arousal deprivation induced a slight, though significant, reduction in adrenal weight. Also, no changes in emotional behavior were noted in stress-exposed groups (5 and 6). Only the interplay between REM-sleep deprivation and stress on the platforms (Groups 7, 8 and especially 9) led to a considerable shift in emotionality.