Life Sciences, Vol. 36, pp. 1275-1280 Pergamon Pre Printed in the U.S.A. BEHAVIORAL STRESSDECREASESPLASMAOXYTOCINCONCENTRATIONSIN PRIMATES Ned H. Kalin *¢, Daniel M. Gibbs ¶ , Charles M. Barksdale ¢, Steven E. Shelton* and Molly Carnes t§ *Psychiatry and @Geriatrics Section, William S. Middleton Memorial Veterans Hospital Madison, Wisconsin and Departments of ~Psychiatry and §Medicine, University of Wisconsin Medical School, Madison, Wisconsin and ¶Department of Reproductive Medicine, UCSD School of Medicine, La Jolla, California (Received in final form January 24, 1985) Summary Using rhesus monkeys, we studied the effects of a beha- vioral stress on plasma concentrations of adrenocorticotropin, oxytocin, and vasopressin. The stress resulted in significant increases in adrenocorticotropin and significant decreases in oxytocin concentrations. No significant changes were seen in vasopressin concentrations. To further explore the relationship between plasma oxytocin and pituitary-adrenal function, dexa- methasone was administered to rhesus monkeys. This resulted in significant increases in plasma oxytocin concentrations, while adrenocorticotropin decreased. Recent evidence suggests that oxytocin (OT) may play an important role in the response to stress. In rats, OT secretion is increased following some, but not all, types of stress (1,2). Oxytocin has been found in high con- centrations in rat hypophysial portal plasma (3) and, like vasopressin (VP), can potentiate the ability of CRF to release ACTH in vitro (4,5). In humans, however, OT has been shown to inhibit stress-induced ACTH secretion (6). Because the rhesus monkey is a useful model in which to study the regula- tion of the neuroendocrine system (7) and results are potentially applicable to humans, we employed this model to investigate the effects of a behavioral stress on plasma OT concentrations in primates. Address correspondence and reprint requests to: Ned H. Kalin, M.D., Psychiatry Section, William S. Middleton Memorial Veterans Hospital, 2500 Overlook Terrace, Madison, WI 53705. 0024-3205/85 $3.00 + .00 Copyright (c) 1985 Pergamon Press Ltd.