CRH and α-helical-CRH modulate behavioral measures of arousal in monkeys

Several neuropeptides involved in the control of pituitary-adrenal activation have also been shown to have behavioral effects which may be mediated by actions on brain mechanisms independent of pituitary release. The behavioral effects of intraventricular administration of CRH and the synthetic peptide antagonist α-helical-CRH were assessed in socially separated squirrel monkeys. Treated monkeys were presented with a sequence of behavioral challenges including undisturbed social separation, presentation of a mirror image, and presentation of a "predator" stimulus. The test sequence was repeated at several time intervals after administration of the peptides. CRH produced dose-related increases in several species-typical measures of arousal including motor activity, vigilance-checking, and marking. Pretreatment with α-helical-CRH prevented the increased motor activity but not the marking behavior associated with CRH. When administered alone, α-helical-CRH increased vigilance-checking. In addition, α-helical-CRH increased aggressive behaviors exhibited at the mirror stimulus. The data provide further support for a central role for CRH in the mediation of both activational and inhibitory behavioral responses to stressful stimuli. These data also suggest both antagonistic and partial agonist effects for α-helical-CRH.