Abstract

The effects of blockade of the beta adrenergic receptors exerted by compound MJ 1999 have been identified in the cardiovascular system of the anesthetized dog. They are as follows: (a) Blockade of the vasodilatation of the hindlimb induced by isoproterenol and by reoxygenation following anoxia: (b) blockade of the cardiac effects of isoproterenol (stimuilation of force of myocardial contraction and coronary vasodilatation) ; and (c) roduction of the coronany vasodilator effect of anoxia. The latter is a combination of blockade of cardliac effects of sympathetic nerve stimulation and release of catecholamines known to occur during anoxia. In the perfused coronary artery of the intact dog and in the coronary vessels of the heartlung preparation, there is a reduction in the vasodilator effect of anoxia.