Objective To observe effect of electroacupuncture at point Neiguan（ PC 6） on myocardial hypertrophy in rats with primary hypertension and to preliminarily explore mediation function of β-adrenergic receptor.Methods Ten male 12-week-old Wistar Kyoto rats（ WKY） were selected as the normal group. Other thirty 12-weekold spontaneously hypertensive rats（ SHR） were selected and randomly divided into a model group

an electroacupuncture group

and a sham-electroacupuncture group

with 10 rats in each. The electroacupuncture group received electroacupuncture at bilateral Neiguan（ 2 /15 Hz

1 m A

for 30 min）

once per day; and the sham-electroacupuncture group only received shallow acupuncture at Neiguan without electrical stimulation. Both groups were intervened for 8 weeks. No treatment was given to the model group. Blood pressure variation condition of rats in each group was monitored adopting noninvasive blood pressure instrument before intervention and in the 2nd

the 4th

the 6th and the8 th week during intervention. Myocardial Hypertrophy index levels of rats in each group were examined with ultrasonic cardiogram after intervention. And the expression of β1-adrenergic receptor（ β1-AR） in cardiac muscle tissue in each group was tested with Western blot. Results 1) Compared with those in the normal group

systolic pressure

diastolic pressure and mean arterial pressure of rats in the model group all remarkably increased（ P < 0. 05）; blood pressure of rats in the electroacupuncture group remarkably decreased compared with that in the model group after being intervened for 6 weeks（ P < 0. 05）. 2) Compared with those in the normal group

left ventricular mass index

left ventricular diastolic end anterior wall thickness

and diastolic end posterior wall depth of myocardial hypertrophy index remarkably increased（ P < 0. 001）

and diastolic end left ventricular diameter remarkably decreased（ P <0. 001） in the model group. 3) Compared with that in the normal group

the expression of myocardial cell β1-AR protein in the model group remarkably increased（ P < 0. 01）. While compared with that of the model group

the expression of myocardial cell β1-AR protein in the electroacupuncture group remarkably decreased（ P < 0. 001）.Conclusion Electroacupuncture at Neiguan（ PC 6） could effectively improve myocardial hypertrophy in rats with primary hypertension. β1-adrenergic receptor might take part in mediating relaxation effects of electroacupuncture at Neiguan on myocardial hypertrophy in SHR rats.