Investigators have hypothesized that brain corticotropin-releasing factor (CRF) systems play an integrative role in an organism's physiological and behavioral response to a stressor. The role of CRF in hypothalamic-pituitary-adrenal (HPA) axis and autonomic function has been extensively investigated, but the data base linking CRF and stress-related behavior is only suggestive. The aim of the proposed research is to determine whether CRF brain systems are involved in the behavioral response to a stressor. To achieve this we will alter central CFR systems in the rat and measure several behavioral responses to stress of varied nature and intensity. To alter CRF systems we will administer CRF, CRF antagonist (CRFa), and CRF antiserum intracerebroventricularly (ICV). Stress will consist of varid intensities of footshock or the anticipation of footshock (i.e., conditioned effects of footshock). In this way both the intensity and nature of the stressor will be manipulated. We will also study the role of central CRF systems in the acquisition of associative learning about stressful events. Finally, we will establish whether the behavioral changes due to altered CRF systems are centrally mediated. In all of the experiments multiple dependent measures will be taken. These will be: locomotion, rearing, grooming, freezing, and antinociceptive behavior. Additionally, we will assess HPA activity with plasma levels of ACTH and corticosterone. This research should ascertain the extent to which endogenous brain CRF systems are involved in the mediation of stress-induced behavior.