Involvement of corticotropin-releasing factor in the retrieval process of fear-conditioned ultrasonic vocalization in rats

The role of the corticotropin-releasing factor (CRF) system in the fear-conditioned ultrasonic vocalizations (USVs) induced by foot shocks in rats was investigated. In the acquisition phase of fear conditioning, the intracerebroventricular administration of CRF receptor antagonist alpha -hCRF attenuated USV responses related to context memory. Even after experiencing eight consecutive days of foot-shock challenges, the alpha -hCRF group emitted similar number of USVs as the control group if they were not given the drug. After the conditioning phase, the groups treated with alpha -hCRF or CRF receptor 1 (CRFR1) antagonist CP-154,526 emitted fewer conditioned USVs than the control group, although there was no difference in the USVs after the shock, which reflected physical stress. These results suggest that the central CRF systems, especially those mediated via CRFR1, are involved in the retrieval process, but not the acquisition or retention processes, of fear-related memory. (C) 2000 Elsevier Science Inc. All rights reserved.