Regulation of the right coronary circulation during a controlled behavioral stress in the conscious dog

Right coronary blood flow (CBF) was measured in 11 mongrel dogs during classical aversive conditioning (a 30 s tone followed by a 1 s 2-6 mA electrical shock). The cardiovascular response consisted of significant (P less than 0.01) increases in: mean arterial pressure (12.9%), systolic right ventricular pressure (RVP, 31.8%), d(RVP)/dt (49.9%) and heart rate (56.2%). The coronary vascular response to behavioral stress consisted of an immediate and significant increase in mean CBF (56.9%) coupled with a significant decrease in mean coronary vascular resistance (CVR, -28.5%). The mean CVR decrease was reduced by cardioselective beta-blockade (CBB) or cardiac pacing and eliminated by right stellectomy (RSGx). The combination of CBB with cardiac pacing resulted in a significant increase in mean CVR. alpha-adrenergic blockade with either phentolamine or prazosin, RSGx, and cardiac pacing significantly reduced the control mean CVR values. Thus, these data suggest that the right coronary response to stress is primarily mediated by the release of metabolic factors secondarily to an increased inotropic or chronotropic state. However, when these metabolic effects were controlled, mean coronary resistance no longer decreased but, rather, increased in response to the aversive stress. This increase could be eliminated by the addition of an alpha-adrenergic antagonist. These data further suggest that the coronary response to behavioral stress activates an alpha-adrenergic vasoconstriction.