Release of catecholamine from the cat heart by some directly and indirectly acting sympathomimetic amines

Abstract

The effect of various directly and indirectly acting sympathomimetic amines on the inotropic, chronotropic and release of noradrenaline was investigated on the isolated cat heart. Tyramine, ephedrine and metaraminol produced positive inotropic and chronotropic effects with simultaneous release of noradrenaline while amphetamine and dopamine were unable to release any significant amount of noradrenaline although they both produced marked cardiac effects. We have further shown that amphetamine produces positive inotropic and chronotropic effects on cat heart depleted of catecholamines by low doses of reserpine, guanethidine and a-methyl tyrosine. It is therefore concluded that amphetamine has a direct effect on the heart and produces its cardiac effect by a different mechanism than that of tyramine.