Objective: To observe the effect of acupuncture of auricular concha area on blood pressure(BP) and to explore its mechanism in lowering BP.Methods: Fifteen spontaneous hypertension rats(SHR) and 22 normal SD rats anesthetized with urethane((1.0 g/kg)) were subjected into the present study.Mean blood pressure of the common cervical artery and activities of the cervical vagus trunk were recorded during electroacupuncture(EA

75-(100 Hz)

dense-sparse waves and duration of(2 min)) or manual acupuncture stimulation(about 2 revolutions/s) of the auricular concha and left "Neiguan"(PC 6).BP and electrical activities of the left vagus and sympathetic nerve were recorded in some rats.Atropine(1%

(0.05 mg/kg)) was injected into the carotid artery for observing the effect of EA on BP. Results: In SHR and normal rats

electrical stimulation and manual acupuncture stimulation of both left and right auricular concha could apparently lower blood pressure of the carotid artery in comparison with the basic values before stimulation(P<0.001);correspondingly

when manual acupuncture stimulation of both left and right auricular concha induced decline of mean pressure

the vagal activity increased and sympathetic discharges decreased clearly.Manual acupuncture stimulation of "Neiguan"(PC 6) could also significantly lower BP

but the effect was remarkably weaker than that of stimulation of auricular concha(P<0.001).In vagotomized and atropine-administrated rats

the effect of acupuncture disappeared

while electrical stimulation of vagus could produce auricular concha-acupuncture-like effects in lowering BP and heart rate.Conclusion: Acupuncture of auricular concha has a definite hypotensive effect in both SHR and normal rats

which depends on the integrity of the vagus in both function and structure.