Objective: To observe the vasorelaxant effects of cyclovirobuxine D on isolated rat thoracic aorta rings and to investigate the possible mechanism. Method: The vasodilation of cyclovirobuxine D at various concentrations (range from 1×10-5 to 6×10-4 mol·L-1) on potassium chloride (KCl) or phenylephrine (PE)-precontracted aorta rings was observed.KCl or PE-induced contraction was also recorded after the aorta rings were preincubated with CVB-D at the concentration of 6×10-4 mol·L-1.When the aortic rings were incubated with different inhibitors

the effect of CVB-D on aortic rings was examined and investigated. Result: In KCl or PE-precontracted aorta rings

CVB-D showed dose-dependent vasorelaxant effect at the given range of concentrations on the rings preconstricted by KCl or PE.Futhermore

CVB-D exhibited stronger vasorelaxation effect on the aorta rings with intacted endothelium compared to the aorta rings denuded endothelium.Additionally

CVB-D preincubation could inhibit KCl or PE-induced contraction

while nitric oxide(NO) synthase inhibitor(L-NAME) or selected NO sensitive soluble guanylate cyclase(sGC) inhibitor 1H-[1]

[2]

[4]-oxadiazolo[4

3-α] quinoxilin-1-one(ODQ) block the vasodilation effect of CVB-D. Conclusion: CVB-D has relaxation effect on rat isolated thoracic arterial rings in a dose-dependent manner

the relaxant effect may be related to the NO-sGC-cGMP(nitric oxide-soluble guanylate cyclase-cyclic guanosine monophosphate) pathway.