Vascular Responses to Catecholamine of the Sinus Node Artery of the Dog

Constant pressure perfusion of the sinus node artery at 100 mmHg was arranged in vagotomized dog heart in situ and adrenergic receptor mechanism of the sinus node artery was studied. Vasoconstrictor and/or dilator responses were obtained when naturally occurring catecholamines, i. e., dopamine, norepinephrine and epinephrine were given intra-arterially. Response to isoproterenol was exclusively vasodilatation. The vasodilator response to the catecholamines was prevented by propranolol, one of the adrenergic blocking agents, while the vasoconstrictor response was abolished by injection of alpha-adrenergic blocking agent, phentolamine or phenoxybenzamine, selectively into the sinus node artery.It was concluded that the existence of both alpha- and beta-adrenergic receptors even in the sinus node artery which is functionally different from the ordinary myocardial arteries.