[Involvement of beta-adrenoceptors in cardioprotective effect of electroacupuncture intervention in mice with swimming fatigue-induced myocardial ischemia].

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 (beta-AR) in the cardioprotective effect of EA intervention.

METHODS: Adult male C 57 BL/6 mice of wild type and beta1/beta2-AR double-knockout (beta1/beta2-AR(-/-)) mice were randomly and respectively divided into control group and EA group, with 8 mice 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 (2 Hz, 0.5 mA) was applied to bilateral "Neiguan" (PC 6) for 30 min, once daily for 7 days in both EA groups. The ST-segment of electrocardiogram (ECG) of standard limb lead II, heart rate were recorded by using a biophysical amplifier and the arrhythmia score was assessed according to Curtis and Walker's methods (1988).

RESULTS: Self-comparison showed that, compared with the baseline, the amplitude of ECG-ST II segment was obviously increased in swimming fatigue C 57 BL/6 mice (P < 0.01) and further obviously increased in beta1/beta2-AR(-/-) mice (P < 0.01), suggesting an acute MI in C 57 BL/6 mice and a worsened MI in beta1/beta2-AR(-/-) mice. Simultaneously, the heart rate was markedly decreased (P < 0.05), and the score of arrhythmia obviously increased in both C 57 BL/6 and beta1/beta2-AR(-/-) mice (P < 0.05). Compared with the modeling procedures, ECG-ST II amplitude and arrhythmia score were significantly decreased in C 57 BL/6 mice of the EA group (P < 0.01, P < 0.05), rather than in the beta1/beta2-AR(-/-) mice of the EA group (P > 0.05). In addition, heart rate levels of both C 57 BL/6 mice and beta1/beta2-AR(-/-) mice had no significant differences between control and EA groups (P > 0.05).

CONCLUSION: EA at "Neiguan" (PC 6) can protect the heart from swimming fatigue-induced MI in C 57 BL/6 mice not in beta1/beta2-AR(-/-) mice, suggesting an involvement of beta1/beta2-AR in the protective effect of EA.