Effects of α1-adrenoceptor gene knockout on the contractile responses in mouse vas deferens (epididymal portion). (a) Representative responses to 100 μM noradrenaline (NA) in WT, AKO, BKO and DKO mice. (b) Contractile responses induced by 100 μM noradrenaline and 1 μM α, β-methylene ATP (α,β-Me ATP). Mean±s.e.mean of 3–6 experiments. *Significantly different from other columns (P<0.01). AKO, α1A-adrenoceptor gene knockout; BKO, α1B-adrenoceptor gene knockout; DKO, α1D-adrenoceptor gene knockout; WT, wild type.