Objective: To investigate the relaxation effects and mechanisms of n-butanolic fraction of Lemonfragrant Angelica Root (LAR) on rat thoracic aorta. Method: Thoracic aortic ring perfusion in isolated ratswas used to observe the effect of n-butanolic fraction on tension changes of aorta rings preshrunk by KCl and norepinephrine (NE). In Ca2+-free kreb's solution

the effects of n-butanolic fraction on Calcium chloride concentration-response curves and the tension changes shrunk by NE were investigated. Confocal laser scanning microscope was used to detect the changes of smooth muscle cells (VSMCs)[Ca2+]i. Result: The n-butanolic fraction of LAR relaxed the KCl and NE-induced contraction of aortic rings

either with or without intact endothelium

in a concentration-dependent manner

and there was no effect on relaxation after after endothelium-denuding. In Ca2+-free solution

n-butanolic fraction of LAR significantly reduced the CaCl2 and NE-induced contraction of aortic rings. Under confocal laser scanning microscope

n-butanolic fraction of LAR (1.22 g·L-1) could inhibit the increase of smooth muscle cells (VSMCs)[Ca2+]i induced by KCl

NE and thapsigargin (TG). Conclusion: n-Butanolic fraction of LAR may relax the tension of aorta rings

probably by inhibiting the influx calcium and calcium release. This study provided evidence for the production techniques of LAR decoction after steam distillation and separating the water-soluble efficacy mark components.