Patterns of Growth Hormone and Cortisol Responses to Psychological Stress in the Squirrel Monkey

Several recent studies have shown that growth hormone (GH) secretion responds acutely to a variety of stressful stimuli in primates. In the present study GH responses to capture, chair restraint, intense sound and aversive conditioning were systematically examined in the squirrel monkey. Plasma cortisol was used as an index of pituitary-adrenal activation. Dissociation of pituitary-adrenal from GH stress responses indicates that specific and separable control mechanisms are involved. An intense sound stimulus was a relatively ineffective stressful stimulus since it was followed by a rise in GH in only 1 of 5 chair restrained animals. During aversive conditioning GH elevation was seen in animals only during training, with no elevation occurring in animals which successfully avoided shock. These findings indicate that growth hormone stress responses are reduced during psychological adaptation. Following capture (which proved to be the most consistently stressful stimulus), levels of both GH and cortisol were significantly higher than resting levels (10.8 vs. 3.9 ng/ml and 755.7 vs. 404.9 μg/100 ml, respectively) ; dissociation of hormone response occurred during chair restraint, with GH falling to resting levels (5.3 ng/ml) and cortisol continuing to rise to a plateau at 60–90 min (1090.6 Mg/100 ml). (Endocrinology 88: 956, 1971)