Coronary vascular sympathetic beta-receptor innervation.
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.
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D003326:Coronary Circulation / Q000187:drug effects; D003331:Coronary Vessels / Q000294:innervation*; D004285:Dogs; D006339:Heart Rate / Q000187:drug effects; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects; D009638:Norepinephrine / Q000494:pharmacology; D011217:Practolol / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D011941:Receptors, Adrenergic; D013233:Stellate Ganglion / Q000502:physiology; D014666:Vasomotor System / Q000187:drug effects / Q000502:physiology*
D000317:Adrenergic alpha-Antagonists; D011941:Receptors, Adrenergic; D011433:Propranolol; D007545:Isoproterenol; D011217:Practolol; D009638:Norepinephrine