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  • Title: Coronary vascular sympathetic beta-receptor innervation.
    Author: Hamilton FN, Feigl EO.
    Journal: Am J Physiol; 1976 Jun; 230(6):1569-76. PubMed ID: 7141.
    Abstract:
    Recent studies indicate that coronary vessels have alpha- and beta-2-adrenergic receptors and that the alpha receptors are functionally innervated. We studied whether the beta-2-vasodilator receptors are functionally innervated, using a dog in situ modified Langendorff preparation with constant coronary perfusion pressure. The beating, nonworking heart and systemic circulation were supported with a pump oxygenator. Stimulation of the left stellate ganglion increased coronary blood flow and decreased coronary sinus oxygen tension from prestimulation control values. After beta-1-receptor blockade (practolol, 10 mg/kg), stellate stimulation decreased coronary blood flow and decreased coronary sinus oxygen tension from prestimulation control values, revealing alpha-receptor vasoconstriction. After the addition of alpha-receptor blockade (Dibozane, 5 mg/kg), stellate stimulation increased coronary blood flow and coronary sinus oxygen tension a small amount from prestimulation values. Finally, after the addition of beta-2-receptor blockade (propranolol, 2 mg/kg), stellate stimulation increased flow and coronary sinus oxygen tension slightly from prestimulation control values. Direct intracoronary injections of isoproterenol, norepinephrine, and epinephrine gave results consistent with the presence of beta-1 myocardial receptors and alpha and beta-2 coronary receptors. We conclude that there is little functional innervation of coronary vascular beta-2 receptors. Intracoronary injections of isoproterenol and epinephrine activated beta-2-receptor coronary vasodilation after beta-1-receptor blockade, but norepinephrine did not.
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