Objective: To study the effect of methanol extract(ME) and ethanol extract(EE) of Terminalia chebula var. tomentella on rabbit thoracic aorta and to discuss the preliminary mechanism. Method: The method of cumulative dosing (concentration of extracts increased from 0.01 g·mL-1 to 0.08 g·mL-1

respectively.) was used to observe the influence on the tension of rabbit thoracic aorta.The effect of extracts of T. chebula var. tomentella(0.01 g·mL-1) on vasoconstrictive action after acetylcholine and phentolamine pretreatment

in the absence of calcium and increasing calcium the effect of extracts T. chebula tomentella(0.01 g·mL-1) on arterial systole was observed under the condition of intracellular calcium release and calcium influx. Result: The influence of ME on contraction extent of isolating thoracic aorta with endothelium was not obvious compared with the thoracic aorta without endothelium(P<0.05). The action of EE was more obvious P<0.05) and showed concentration dependent. ME(0.01 g·mL-1) and EE(0.01 g·mL-1) all depressed the predilated vascular strips by acetylcholine-induced(1×10-5 mol·L-1) and phentolamine-induced(10 mg·L-1)

respectively. The vasoconstrictor effect of ME(0.01 g·mL-1) was inhibited by verapamil. In the absence of Ca2+ solution

the contraction amplitude in endothelium-denuded aorta rings treated by ME(0.01 g·mL-1) was significantly lower than those of contraction in Ca2+ solution(P<0.05). Conclusion: ME and EE has contraction effect on rabbit thoracic aorta and the mechanism of vasoconstrictor effect may be in connection with M receptor

α-receptor and Ca2+.