The involvement of perivascular innervation in acetylcholine-induced endothelium-dependent vascular relaxation in the rat superior mesenteric arterial bed.

The distribution of the ability of perivascular peptidergic innervation to influence acetylcholine-induced relaxation in the arterial bed has been investigated using the superior mesenteric arterial bed of the rat. The superior mesenteric artery was denervated by freezing, under pentobarbital anaesthesia (40 mg/kg i.p.), at one of two different points and the animals allowed to survive for 7, 14, 21 or 28 days following freezing. This produced a range of denervation along the superior mesenteric artery and its branches. The ability to respond to acetylcholine in an endothelium-dependent fashion was determined pharmacologically in isolated perfused superior mesenteric artery preparations. The extent of the denervation was determined by immunohistochemistry. It was found that the ability of the arterial bed to relax in a concentration-dependent manner to increasing concentrations of acetylcholine was little altered by denervation of the superior mesenteric artery alone. However when a short piece of the superior mesenteric artery and its primary branches were denervated the response to acetylcholine was reduced. It is concluded that the innervation of the primary branches of the mesenteric artery, the jejunal and ileal branches, contributes to the ability of acetylcholine to cause endothelium-dependent relaxation.