[Effect of dopamine on coronary circulation]

The effect of dopamine on coronary and systemic circulation was examined in an experimental study on dogs using catheterization and extracorporeal perfusion of the bypassing branch of the left coronary artery, and simultaneous recording of heart's vascular resistance as well as cardio- and hemodynamic patterns. Dopamine introduced into coronary perfusion flow caused a dilatation of coronary vessels, a reflex drop in arterial blood pressure and peripheral vascular resistance, and changes in heart rate and intensity of cardiac contractions. Dopamine dosage should be about ten times as high to reproduce cardiodynamic and hemodynamic effects, comparable with the response to adrenaline and noradrenaline in terms of magnitude and pattern of development. Coronary vessels are dilated in two steps, through cholinergic activation and direct stimulation of beta-adrenoreactive systems. These two phases can be blocked by atropine and obsidan, respectively. After m-cholinergic and beta-adrenoreactive systems are blocked, dopamine produces a slight coronary vasoconstriction.