[Does the Nucleus Ambiguus-Vague Nerve Mediate Anti-myocardial Ischemic Effect of Electroacupuncture of "Neiguan" (PC 6)-"Jianshi" (PC 7) in Myocardial Ischemia Rats].

Objective: To observe the effect of electroacupuncture (EA) stimulation of "Neiguan" (PC 6)-"Jianshi" (PC 7) on ischemic myocardial injury in myocardial ischemic (MI) rats, so as to explore its mechanism underlying improvement of MI.

Methods: A total of 48 male Wistar rats were randomly divided into normal, MI model, PC 6-PC 7, Sanyinjiao-Diji (SP 6-SP 8) groups (=8 in each group for physiological experiments, =4 in each group for immunoflorescence stain). The MI model was established by occlusion of the anterior descending branch of the left coronary artery. Electrocardiogram (ECG) of the neck-thoracic lead was recorded and the heart rate variability (HRV) analyzed by using a physiological signal collecting system (MP 150) and PowerLab software. EA (2 Hz/15 Hz, 0.5 mA) was applied to bilateral PC 6-PC 7 or SP 6-SP 8 for 30 min every time, on the 1,2,3 day after modeling. Serum creatine kinase-MB isoenzyme (CK-MB) and lactate dehydrogenase-1 (LDH 1) and endothelin (ET) contents were assayed by ELISA. The expression of choline acetyltransferase (ChAT) and vesicular acetylcholine transporter (VAChT) and proteins in the nucleus ambiguus (NA) region of the medulla oblongata was detected by immunofluo-rescence stain.

Results: Compared with the normal group, the ECG J-point height (1 h), serum CK-MB, LDH 1 and ET contents (1 d and 3 d), HR (1 h and 1 d) and LF/HF levels of HRV (1 h, 1 d and 3 d) and the number of positive neurons (3 d) in the NA region were significantly increased in the model group (<0.01, <0.05), while HF levels (1 h, 1 d and 3 d) and ECG J-point height (1 d and 3 d) were considerably decreased after MI. After EA intervention, the ECG J-point height 3 d after MI was close to zero in both PC 6-PC 7 and SP 6-SP 8 groups, being better than that (negative value) of the model group, and serum CK-MB, LDH 1 and ET contents (1 d, 3 d) of both EA groups, and HR (1 d) and LF/HF (3 d) of the PC 6-PC 7 group were obviously down-regulated (<0.01, <0.05), and the decreased HF 3 d post-MI and the increased number of positive neurons were significantly up-regulated in the PC 6-PC 7 group (<0.01). No significant differences were found between the two EA groups in raising J-point height and in down-regulating serum CK-MB, LDH 1 and ET contents (>0.05). Compared with the model group, no significant changes were found in HR 1 d post-MI of the SP 6-SP 8 group, 3 d post-MI of both EA groups, in HF 3 d post-MI of the SP 6-SP 8 group, in LF/HF 1 d post-MI of both EA groups and 3 d post-MI of the SP 6-SP 8 group, in the number of positive neurons of the SP 6-SP 8 group, and ChAT and VAChT positive neurons of both EA groups (>0.05).

Conclusions: EA intervention may improve ischemic myocardial injury in MI rats, probably by activating neurons in the NA region, and enhancing the cardiac parasympathetic tension, and balancing cardiac sympathetic/parasympathetic nerve activities, but the effect of cholinergic neurons of NA needs being studied further.