Antagonistic effects of antimuscarinic drugs on α1-adrenoceptors

We previously observed that noradrenaline (NA)-induced contraction of the portal vein of rabbit was relaxed by the antimuscarinic drugs of atropine sulfate, but not scopolamine hydrobromide. In the present study we examined the possible effect of the antimuscarinic drugs of atropine sulfate, scopolamine hydrobromide, p-fluoro-hexa-hydro-sila-difenidol (p-F-HHSiD, the M3-receptor antagonist) and pirenzepine (the M1-receptor antagonist) on α1-adrenoceptor (AR).