Objective: To observe the cardioprotective effects of repetitive pretreatment of electroacupuncture(EA) at higher intensity prior to the myocardial ischemia and reperfusion(MI/R) and to explore the involvement of beta-adrenergic receptor.Methods: Male SD rats were evenly randomized into normal control(NC)

model

EA and EA+ propranolol groups.MI/R model was produced by occlusion of the anterior descending branch of the left coronary artery((30 min)) and reperfusion((10 min)) in the rats.ECG ST-segments and the ratio of infarct size/risk zone were detected

and the content of cardiac beta_1-adrenoceptor was assayed with immunoblot technique.EA((20 V)

(20 Hz)) was applied to bilateral "Neiguan"(PC 6) for(30 min)

once daily and continuously for 3 days.Propranolol((10 mg/kg)

i.p) was given to the animals(15 min) before EA every time.Results: The elevated ST-segments of ECG in IR group recorded 30 min after ischemia and 10 min after reperfusion were significantly higher than those of NC group(P<0.01 and P<0.01 respectively);in EA group the elevated ST-segments were markedly reduced(P<0.01 and P<0.01 respectively vs IR group);while the elevated ST-segments in EAP group were almost the same as IR group

much higher than EA group(P<0.01 and P<0.01 respectively).The similar results were also achieved in the ratios of infarct size/risk zone in the 4 groups.Moreover

the content of cardiac beta_1-adrenoceptor(CCA) in EA group was significantly reduced as compared with IR group(P<0.01) in which CCA was significantly higher than NC group(P<0.01).In EAP group the CCA was almost the same as that in IR group(P>0.05) and much higher than EA group(P<0.05).Conclusion: The results of the present study indicate that by mimicking the ischemic preconditioning

pretreatment of EA can protect the heart from injury of MI/R in rats.The protective effect of EA is mediated by cardiac beta_1-adrenoceptor.