Venous and arterial responses to norepinephrine in dogs treated with reserpine

Abstract

Experiments were done to see if the effects of norepinephrine upon veins, arteries, and small vessels are augmented in dogs after treatment with reserpine. With intra-arterial injection of increasing doses of norepinephrine into the perfused foreleg there were progressive increments in total, arterial, small vessel, and venous resistances. In animals treated with reserpine the increments in total and small vessel resistances were greatly augmented while increments in segmental arterial resistance were increased only slightly. The venous responses in these treated dogs were not augmented. Similar effects on segmental resistances were noted with infusion of norepinephrine into a systemic vein. The vasoconstrictor effect of tyramine was reduced in treated dogs and was restored after intra-arterial and intravenous norepinephrine. The results indicate that veins do not participate in the increased vascular responsiveness to norepinephrine which occurs in forelegs of dogs after treatment with reserpine.