Objective: To observe the effect of electroacupuncture (EA) stimulation of the Heart Meridian on electrical activities of neck sympathetic and vagal nerves in acute myocardial ischemia (AMI) rats.
Methods: Thirty SD rats were randomly divided into 3 groups, sham operation (sham), model and EA(n=10 rats in each group). The left anterior descending branch (LADB) of the coronary artery was occluded to make an acute myocardial ischemia (AMI) model.For rats of the sham group, a surgical suture was simply threaded beneath the LADB without ligation. EA stimulation (2 Hz, 1 mA)was applied to bilateral "Shenmen" (HT 7), "Tongli" (HT 5) and the middle-point between HT 7 and HT 5 for 20 min. The electrical activities of the left cervical sympathetic and vagal nerves were recorded using a bipolar platinum wire electrodes and a BIOPAC MPl 50 system, and the electrocardiogram (ECG) of the standard limb lead Ⅱ was recorded simultaneously. The AMI severity was evaluated by using J-spot height of ECG.
Results: After AMI, the heart rate (HR), J-spot of ECG, and the discharge frequency of the cervical sympathetic nerve were significantly increased in the model group compared with the sham group (P<0.01), while the discharge frequency of vagal nerve was obviously decreased (P<0.01). Following EA stimulation, the increased levels of HR, J-spot height and discharge frequency of sympathetic nerve, and the decreased discharge frequency of vagus were significantly suppressed at time-points of 1, 3, 5 and 15 min after EA (P<0.01). In addition, the ratio of discharge frequencies of vagal/sympathetic nerves was notably down-regulated after AMI (P<0.01). After EA stimulation, the ratios of vagal/sympathetic discharge at the time-points of 1, 3, 5 and 15 min following EA were significantly increased (P<0.01).
Conclusions: EA stimulation of the Heart Meridian may improve AMI by inhibiting sympathetic discharges and elevating vagal discharges in AMI rats, i.e., coordinating activities of the autonomic nerve systems.