Interaction of papaverine and isoproterenol in the vascular system of the dog and intestinal smooth muscle of the rabbit.

It was found that the effect of isoproterenol on the vasculature of the anesthetized dog can be potentiated by previous administration of papaverine. This effect is apparent in spite of concomitant potentiation of inotropic and/or chronotropic effects, which tend to obscure the vasomotor effect. Evidence is presented supporting the hypothesis that papaverine interacts with receptors of the vascular tree, which are usually classified as beta receptors and are responsive to isoproterenol. Evidence is presented showing almost complete inhibition of the chronotropic effects of papaverine by propranolol, and a synergism of papaverine with the chronotropic effects of isoproterenol. Evidence was obtained using the intestinal smooth muscle of the rabbit in support of the hypothesis linking mediation of the beta adrenergic system to papaverine effects.