Plasma cortisol and appetitively motivated arousal in monkeys.

A disagreement exists in the literature as to whether plasma glucocorticoids are a sensitive index of emotional arousal. In order to provide further data on this subject, arousal in adult male rhesus monkeys was produced by classical appetitive conditioning done once every 48 hr. Monkeys showed significantly more aroused behavior during CS+ sessions than during CS- sessions. Concurrent with these behavioral changes, appetitive conditioning suppressed the increase in plasma cortisol that took place in control conditions. This dissociation between cortisol and arousal provides additional data for the conclusion that plasma glucocorticoids are an insensitive index of arousal. The fact that glucocorticoids decrease dramatically under similar experimental conditions in rats suggests that hormonal regulatory mechanisms for this rodent species may differ from that for primates.