An Official Journal of the American Heart Association BRIEF REVIEWS Adrenergic Responses of the Coronary Vessels

THE EFFECTS of stimulation of the cardiac sympathetic nerves and of circulating catecholamines on the heart and coronary circulation have been studied extensively for more than 80 years. The biochemical, electrophysiological, and mechanical responses of the myocardium have been described in considerable detail but surprisingly little is known about the adrenergic responses of the coronary vessels. This is because of the difficulty in separating the direct actions of adrenergic agents on coronary smooth muscle tn the intact animal from the secondary effects induced by the almost simultaneous changes in transmural pressure and myocardial metabolism. A common approach to the problem of separating these effects has been to use adrenergic agents which selectively stimulate or block specific myocardial or coronary adrenotropic receptors. It therefore is appropriate to begin with a brief outline of the classification of these receptors.