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 innervatio n to influence acetylcholine-induced relaxation in the arterial bed ha s 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 poi nts and the animals allowed to survive for 7, 14, 21 or 28 days follow ing freezing. This produced a range of denervation along the superior mesenteric artery and its branches. The ability to respond to acetylch oline in an endothelium-dependent fashion was determined pharmacologic ally 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 concentra tion-dependent manner to increasing concentrations of acetylcholine wa s little altered by denervation of the superior mesenteric artery alon e. However when a short piece of the superior mesenteric artery and it s primary branches were denervated the response to acetylcholine was r educed. It is concluded that the innervation of the primary branches o f the mesenteric artery, the jejunal and ileal branches, contributes t o the ability of acetylcholine to cause endothelium-dependent relaxati on.