Anxiogenic effect of corticotropin-releasing hormone in the dorsal periaqueductal grey.

To investigate whether the dorsal periaqueductal grey (DPAG) might be involved in the anxiogenic effect of intracerebroventricular (i.c.v.) administered corticotropin-releasing hormone (CRH), rats (n = 6-13) received microinjections into the DPAG of CRH (1 or 2 microg) or saline and were tested on the elevated plus maze. The drug caused a dose-dependent decrease in plus maze exploration (percentage of entries into open arms: saline 31.9 +/- 8.6, CRH 1 microg 19.2 +/- 4.0, CRH 2 microg 6.9 +/- 3.7; p < 0.01, ANOVA). In a second experiment the anxiogenic effect of intra-DPAG CRH (2 microg) was prevented by previous microinjection of alpha-helical-CRH(9-41) (0.5 microg), a CRH antagonist (percentage of entries into open arms: saline + CRH 20.3 +/- 3.7, alpha-helical-CRH(9-41) + CRH 45.7 +/- 1.6). These results suggest that the DPAG may be a site of the anxiogenic effect of i.c.v. injected CRH.