Static exercise in anesthetized dogs, a cause of reflex alpha-adrenergic coronary vasoconstriction.

The coronary blood flow and vascular resistance responses to static hindlimb exercise were studied in 11 anesthetized dogs after beta- and combined alpha- and beta-adrenergic blockade to determine if this stress causes coronary vasoconstriction. After beta-blockade static exercise increased the blood pressure and double product, but decreased the right and left ventricular (LV) coronary blood flow and increased the coronary vascular resistance. These vascular changes primarily occurred in the epicardial and mid-myocardial but not the endocardial layers of the LV. Following combined alpha- and beta-adrenergic blockade, the systemic hemodynamic and coronary flow and resistance changes were abolished. These data suggest that alpha-adrenergic mediated coronary vasoconstriction occurs during static hindlimb exercise in dogs.