A Comparison of the Effects of Cocaine in Arterial and Venous Smooth Muscle Responses to Vasoactive Stimuli 1

Abstract

Summary

Cocaine (2.3 × 10~^6- M) enhanced the contractile responses of super-fused mesenteric arteries, and cutaneous arteries and veins to norepinephrine. This effect was probably related to inhibition of the neuronal catecholamine reuptake mechanism and not to nonspecific supersensitivity since the contractile responses to tyramine were significantly reduced but the contractile responses to barium and potassium chlorides essentially unchanged. The adrenergic nerves of these blood vessels were confined to a dense innervation in the region of the adventitial medial border with some nerves apparently present in the outer portion of the media (dorsal metatarsal vein). In contrast to these findings, the anterior mesenteric veins responded only with a small response to tyramine, which was inhibited by cocaine. However, the contractile responses to norepinephrine were not enhanced 30 min after the addition of cocaine to the superfusate. The anterior mesenteric vein displayed a sparse and diffuse adrenergic innervation. It was concluded that the inability of cocaine to enhance the contractile responses of mesenteric veins to norepinephrine resulted from the sparse distribution of the nerve endings in this vein and perhaps from a difference in the neuronal membrane adrenergic amine reuptake mechanism.