Anxiolytic effect of a CRH receptor antagonist in the dorsal periaqueductal gray

Corticotropin-releasing hormone (CRH) is anxiogenic when microinjected into the dorsal periaqueductal gray (DPAG), Microinjection of alpha-helical-CRH 9-41 (0.5 mug) a CRH receptor antagonist, however, failed to change anxiety levels. The objective of this study was to verify, if this compound has an y effect in the anxiogenic behavior of mts submitted to 4 hr of restraint s tress 24 hr before the test in an elevated plus maze. Results showed that s tressed rats had a decreased exploration of open arms without changing the number of enclosed arm entries. The stress effect was reversed by intra-DPA G injection of alpha-helical-CRH9-41 (0.5 mug). These results suggest that the anxiogenic behavior of rats previously stressed by forced immobilizatio n might involve facilitation of CRH-mediated neurotransmission in the DPAG, (C) 2000 Wiley-Liss, Inc.