Abolition of reactive hyperemia in the dog heart following alpha adrenergic blockade and its reversal by vasopressin.

The local intracoronary application of the alpha adrenergic blocking agents phenoxybenzamine or dibenamine, in open chest anesthetized dogs, regularly resulted in maximal coronary vasodilatation thus abolishing reactive hyperemia. Infusion of vasopression or angiotensin returned coronary flow to near control levels and restored reactive hyperemia. It is thus concluded that although alpha blocking agents can relax coronary vessel smooth muscle, reactive hyperemia does not appear to be mediated through the inhibition of alpha adrenergic constrictor tone.