Stimulation of the left stellate ganglion after sequential receptor blockades revealed little functional innervation of coronary vascular beta-2 receptors in a dog model.
Are coronary vascular beta-2-vasodilator receptors functionally innervated?
This preclinical study demonstrates that there is little functional innervation of coronary vascular beta-2 receptors in a dog model.
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.
Fn et al. (Tue,) conducted a other in Coronary vascular sympathetic beta-receptor innervation. Stellate ganglion stimulation and sequential receptor blockades vs. prestimulation control values was evaluated on Coronary blood flow and coronary sinus oxygen tension. Stimulation of the left stellate ganglion after sequential receptor blockades revealed little functional innervation of coronary vascular beta-2 receptors in a dog model.