Objective To observe the cardioprotective effect of electroacupuncture(EA)stimulation at"Neiguan"(PC 6)in mice with myocardial ischemia(MI)and to explore the involvement of cardiac beta-adrenergic receptors(β-AR)in the cardioprotective effect of EA intervention.Methods Adult male C 57BL/6mice of wild type andβ1/β2-AR double-knockout(β1/β2-AR-/-)mice were randomly and respectively divided into control group and EA group

with 8mice in each group.These mice were subject to procedures of basic control

fatigue swimming and fatigue swimming+EA.The model was established by fatigue swimming for inducing acute MI.EA(2Hz

0.5mA)was applied to bilateral"Neiguan"(PC 6)for 30min

once daily for 7 days in both EA groups.The ST-segment of electrocardiogram(ECG)of standard limb leadⅡ

heart rate were recorded by using a biophysical amplifier and the arrhythmia score was assessed according to Curtis and Walker's methods(1988).Results Selfcomparison showed that

compared with the baseline

the amplitude of ECG-STⅡsegment was obviously increased in swimming fatigue C 57BL/6mice(P<0.01)and further obviously increased inβ1/β2-AR-/-mice(P<0.01)

suggesting an acute MI in C 57BL/6mice and a worsened MI inβ1/β2-AR-/-mice.Simultaneously

the heart rate was markedly decreased(P<0.05)

and the score of arrhythmia obviously increased in both C 57BL/6andβ1/β2-AR-/-mice(P<0.05).Compared with the modeling procedures

ECG-STⅡ amplitude and arrhythmia score were significantly decreased in C 57BL/6 mice of the EA group(P<0.01

P<0.05)

rather than in theβ1/β2-AR-/-mice of the EA group(P>0.05).In addition

heart rate levels of both C 57BL/6mice andβ1/β2-AR-/-mice had no significant differences between control and EA groups(P>0.05).ConclusionEA at"Neiguan"(PC 6)can protect the heart from swimming fatigue-induced MI in C 57BL/6mice not inβ1/β2-AR-/-mice

suggesting an involvement ofβ1/β2-AR in the protective effect of EA.