Regional coronary vasoconstriction in response to stimulation of stellate ganglia

Recent experiments have demonstrated that direct and reflex sympathetic stimulation elicit coronary vasoconstriction when the inotropic and chronotropic effects are blocked with beta-adrenergic blocking agents. This vasoconstriction can be blocked with alpha-adrenergic blocking agents. Regional variations in the flow reduction produced by right (RSS) vs. left (LSS) stellate stimulation were delineated in this study. Open-chest pentobarbital-anesthetized dogs were given propranolol (1 mg/kg iv). Hearts were neurally decentralized and paced just above the spontaneous heart rate. Radiolabeled microspheres (15 +/- 2 micrometers) were injected into the left atrium before and during RSS (n = 11) or LSS (n = 11). RSS produced relatively little vasoconstriction confined to anterior left ventricle. In contrast, LSS produced significant vasoconstriction in all areas of the right and left ventricles. In the endocardial half of the left ventricle the flow decrease was uniformly distributed among the regions studied. In the epicardial half of the flow decrease was more pronounced in posterior than in anterior regions. No significant change occurred in the endo-epi ratios with RSS, but with LSS there was a significant change in three areas. The changes were related to regional variations in the degree of epicardial constriction. Thus RSS and LSS have differential effects (quantitatively) on regional coronary blood flow.