CRH antagonists (A, α-helical CRH; B, CP-154,526) block shock-induced freezing to the same degree in both WT and CRH KO mice. After i.c.v. administration of vehicle followed by 3 foot shocks (1-s duration every 20 s), the two genotypes exhibit similar amounts of freezing (A, Vehicle; B, Vehicle). i.c.v. administration of two chemically unrelated CRH antagonists, either the nonselective α-helical CRH9–41 (A, alpha-helical CRH) or the CRH type I receptor-specific CP-154,526 (B, CP-154,526) significantly blocks shock-induced freezing to the same degree in WT and CRH KO mice. In A–B, WT, closed bars; CRH KO, open bars.