Objective: To evaluate vasorelaxant and vasoconstriction effects of Zingiber officinale vat.rubrum (ZOVR) on live rats and isolated aortic rings of spontaneously hypertensive rats (SHRs).Methods: Extracts of ZOVR were subjected to in-vivo antihypertensive screening using noninvasive blood pressures in SHRs.The most potent extract,ZOVR petroleum ether extract (ZOP) was then fractionated using n-hexane,chloroform and water.Isolated thoracic aortic rings were harvested and subjected to vascular relaxation studies of n-hexane fraction ofZOP (HFZOP) with incubation of different antagonists such as Nω-nitro-L-arginine methyl ester (L-NAME,10 μmol/L),indomethacin (10 μmol/L),methylene blue (10 μmol/L),atropine (1 μmol/L),glibenclamide (10 μmol/L),prazosin (0.01 μmol/L),and propranolol (1 μmol/L).Results: During the screening of various ZOVR extracts,ZOP produced the most reduction in blood pressures of SHRs and so did HFZOP.HFZOP significantly decreased phenylepbrine-induced contraction and enhanced acetylcholine-induced relaxation.L-NAME,indomethacin,methylene blue,atropine,and glibenclamide significantly potentiated the vasorelaxant effects of HFZOP.Propranolol and prazosin did not alter the vasorelaxant effects of HFZOP.HFZOP significantly suppressed the Ca2+-dependent contraction and influenced the ratio of the responses to pbenylephrine in Ca2+-free medium.Conclusion: This study demonstrates that ZOP may exert an antihypertensive effect in the SHR model.Its possible vascular relaxation mechanisms involve nitric oxide and prostacyclin release,activation of cGMP-KATP channels,stimulation of muscarinic receptors,and transmembrane calcium channel or Ca2+ release from intracellular stores.Possible active compounds that contribute to the vasorelaxant effects are 6-gingerol,8-gingerol and 6-shogaol.