Abstract: AimTo study the vasodilation effect of atropine and its mechanism.MethodsIsometric tension was recorded in isolated rat super mesenteric arteries precontracted by noradrenaline (NE) to study the vasodilation effect of atropine, and to investigate the role of endothelial cell and vascular smooth muscle cell on vasodilation.ResultsAtropine was shown to significantly dilate the endothelium-intact and endothelium-denuded arteries precontracted by NE.N^ω-Nitro-L-arginine methyl ester (L-NAME, nitric oxide synthase inhibitor), indomethacin (cyclooxygenase inhibitor), propranolol (general β adrenoceptor antagonist ) and glibenclamide (ATP sensitive potassium channel inhibitor) showed no effect on vasodilation of atropine.Atropine did not affect the concentration-contraction curve of K⁺.However, atropine suppressed the contraction induced by NE and CaCl₂, but not that by caffeine in the Ca²⁺-free Krebs solution.ConclusionAtropine showed significant vasodilation effect which may derive, in part, from endothelium.Besides, atropine could inhibit the receptor-mediated Ca²⁺-influx and Ca²⁺-release, which was inferred to the mechanism of atropine on vasodilation.