Castration attenuates prolactin response but potentiates ACTH response to conditioned stress in the rat.

The purpose of this study was to examine the effect of circulating androgens on neuroendocrine, autonomic, and behavioral responses to stress. The effects of conditioned stress were studied in male Sprague-Dawley rats that were intact, gonadectomized, or gonadectomized and treated with dihydrotestosterone (DHT). Intact animals received sham surgeries. Animals were stressed 3 wk after surgery. The adrenocorticotropic hormone (ACTH) response to conditioned stress was significantly potentiated (P < 0.01) in gonadectomized males compared with sham-operated and gonadectomized DHT-treated animals. In stressed rats, plasma corticosterone levels were significantly higher (P < 0.05) in gonadectomized animals compared with DHT-treated castrates. The prolactin response to stress was decreased (P < 0.01) in gonadectomized males compared with sham-operated and gonadectomized DHT-treated rats. The stress-induced increases in plasma renin activity and concentration were not altered in gonadectomized or in gonadectomized DHT-treated animals. Nonstressed DHT-treated castrates exhibited more "fearlike" behavior compared with nonstressed sham-operated and gonadectomized animals. However, conditioned stress produced the same behavioral effects in all treatment groups. The results demonstrate that the ACTH/corticosterone, prolactin, and behavioral responses to a psychological stressor are differentially regulated by circulating androgens.