Asymmetry of responses to norepinephrine in perfused resistance arteries.

Diameter constrictor responses were significantly greater when norepinephrine (NE) was delivered intraluminaly compared to extraluminal application in isolated perfused mesenteric resistance arteries of the rat. The difference in response via the two routes was abolished by cocaine, a neuronal uptake blocker. Endothelium removal enhanced NE-induced constrictions but responses remained significantly greater when delivered intraluminally. This study provides evidence of asymmetry of vascular smooth muscle in resistance arteries due to a greater neuronal uptake of NE on the adventitial surface.