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) rece ived microinjections into the DPAG of CRH (1 or 2 mu g) or saline and were tested on the elevated plus maze. The drug caused a dose-dependen t decrease in plus maze exploration (percentage of entries into open a rms: saline 31.9 +/- 8.6, CRH 1 mu g 19.2 +/- 4.0, CRH 2 mu g 6.9 +/- 3.7; p < 0.01, ANOVA). In a second experiment the anxiogenic effect of intra-DPAG CRH (2 mu g) was prevented by previous microinjection of a lpha-helical-CRH9-41 (0.5 mu g), a CRH antagonist (percentage of entri es into open arms: saline + CRH 20.3 +/- 3.7, alpha-helical-CRH9-41+CR H 45.7+/-1.6). These results suggest that the DPAG may be a site of th e anxiogenic effect of i.c.v. injected CRH.