Vascular and myocardial effects of mecinarone.

The effects of mecinarone on the contractions induced by noradrenaline, potassium and calcium were studied with the isolated aorta and central artery of the rabbit ear. In our experimental conditions mecinarone was found to act as a competitive antagonist of calcium. It preferentially inhibited the noradrenaline-evoked contraction induced in the rabbit ear artery and had a smaller effect on the extracellular calcium-induced contraction of depolarized arterial smooth muscle. In the isolated guinea pig heart, mecinarone produced a reversible decrease in the rate of rise of the ascendant phase of the action potential without significantly changing the resting potential. In hearts inactivated by depolarisation, mecinarone inhibited the contractions restored by isoproterenol without suppressing the calcium action potential. These results suggest that the mode of action of mecinarone is different from that of verapamil or nifedipine but is comparable to that of chlorpromazine, although mecinarone has no sedative effect.