Frustrative nonreward and pituitary-adrenal activity in squirrel monkeys

Little is known about frustration-induced changes in stress physiology in h umans and nonhuman primates. Here we assess in two experiments with squirre l monkeys plasma levels of pituitary-adrenal stress hormones in conditions designed to provoke frustrative nonreward. In the first experiment 18 prepu bertal monkeys were trained to feed from one of eight sites, and then teste d without food at any of the sites. These monkeys responded with significan t increases in cortisol and adrenocorticotropic hormone (ACTH). In the seco nd experiment 18 adult monkeys were trained to feed from one of eight sites , and then tested after food was moved to a different foraging site. Nine m onkeys found food at the relocated site, discontinued foraging at the previ ously baited site, and responded with decreases in cortisol. The other nine monkeys failed to find the relocated site, initially increased their visit s to the previously baited site, and responded with elevations in cortisol and ACTH. In keeping with comparable findings in rats, our observations ind icate that frustrative nonreward elicits ACTH-stimulated secretion of corti sol in primates. (C) 2000 Elsevier Science Inc. All rights reserved.