Objective To observe the effect of different strength of acupuncture stimulation on blood pressure and plasma endothelin(E)-1 in spontaneous hypertension rats(SHR)

so as to seek a better acupuncture parameter for clinical treatment of hypertension.Methods Twenty-eight 9-week-old SHRs were randomized into mild-stimulation group

moderate-stimulation group

strong-stimulation group and model group(n=7 in each group).Seven normotensive SD rats served as a normal control group.Acupuncture stimulation with mild

moderate and strong stimulation was applied to bilateral "Taichong"(LR3) for 5 min

once daily for 7 days.Blood pressure(BP) was determined by using a non-invasive BP-6 detection system.Plasma ET-1 was assayed by radioimmunoassay.Results Compared with the model group

the systolic pressure of the moderate-stimulation group on the 6th and 7th day was decreased significantly after acupuncture of "Taichong"(LR 3)(P<0.01)

being significantly lower than that of the mild-and strong-stimulation groups(P<0.01).In comparison with the normal control group

plasma ET-1 level in the model group was increased significantly(P<0.01)

while compared with the model group

only that in the moderate-stimulation group was down-regulated considerably(P<0.01).No significant differences were found between the mild-stimulation and model groups

between the strong-stimulation and model groups

and between the mild-stimulation and strong-stimulation groups in plasma ET-1 level(P>0.05).Conclusion Moderate-stimulation of "Taichong"(LR3) can lower blood pressure and plasma EA-1 level in spontaneous hypertension rats.The reduced level of plasma ET-1 may be one of its mechanisms underlying improving hypertension.