Alpha-helical CRF(9-41) prevents anxiogenic-like effect of NPY Y1 receptor antagonist BIBP3226 in rats.

We reported previously that the neuropeptide Y (NPY) Y1 receptor antagonist, N2-(diphenylacetyl)-N-[(4-hydroxy-phenyl)methyl]-D-arginine amide (BIBP3226) has an anxiogenic-like effect in the elevated plus maze test in rats. In this study we investigated the effect of the corticotropin-releasing factor (CRF) receptor antagonist, alpha-helical-CRF(9-41) (alpha-h-CRF) on this response. BIBP3226 (5 microg, i.c.v.) induced an anxiogenic-like effect, which was blocked by pretreatment with alpha-h-CRF at a concentration (1 microg, i.c.v.) which alone failed to affect the elevated plus maze performance. Thus, the anxiogenic effect of a selective Y1 receptor blocker was prevented by the blockade of CRF receptors, suggesting antagonistic effects of endogenous NPY and CRF in shaping the response to novelty.