Evidence for the possible involvement of Ca2+ entry blockade in the relaxation by class I antiarrhythmic drugs in the isolated pig coronary smooth muscle.

Effects of several Na+ channel blockers (i.e., class I antiarrhythmic agents), procainamide, quinidine, lidocaine, mexiletine, propafenone, were investigated in the isolated endothelium-denuded pig coronary artery focusing on the possible involvement of the blockade of Ca2+ channels and/or opening of K+ channels in the relaxant responses.