Effects of electroacupuncture on sympathetic nerve-related substance in myocardial tissue in mice with myocardial ischemia

Abstract

To observe the effects of electroacupuncture (EA) on sympathetic nerve-related substance in myocardial tissue in mice with myocardial ischemia (MI), and to explore its possible mechanism. Thirty adult male C57BL/6 mice were randomly divided into a sham operation group, a model group and an EA group, 10 mice in each one. The model of MI was established in the model group and EA group by ligating the left anterior descending branch of coronary artery. The mice in the sham operation group were not treated with ligating at left anterior descending branch of coronary artery, but the remaining procedure was similar with the model group. The mice in the EA group were treated with EA at "Neiguan" (PC 6) with 2 Hz/100 Hz of frequency and 2 mA of intensity, 20 min per treatment, once a day for totally 5 days. No EA was given for model group and sham operation group. The electrocardiogram was recorded and △ST value was calculated to evaluate the model. TTC staining was applied to evaluate the infarct size. Immunohistochemical (IHC) method was applied to evaluate the positive nerve fiber density in myocardial tissue. Western blot method was applied to test the protein expression levels of neuregulin-1 (NRG-1), tyrosine hydroxylase (TH), growth associated protein-43 (GAP-43). The electrocardiogram (lead II) results indicated compared with the sham operation group, the S-T segments in the model group and EA group were increased obviously (both P<0.01), indicating the MI model was established successfully. The TTC staining results indicated compared with sham operation group, the infarction size was significantly increased in the model group (P<0.01); compared with the model group, the infarction size in the EA group was significantly reduced (P<0.01). The IHC results indicated compared with the sham operation group, the positive nerve fiber density in myocardial was increased in the model group (P<0.01); compared with the model group, the positive nerve fiber density in myocardial was reduced in the EA group (P<0.05). The Western blot results indicated compared with the sham operation group, the expression levels of TH, NRG-1 and GAP-43 were significantly increased in the model group (P<0.01); compared with the model group, the expression level of TH and GAP-43 were significantly reduced (P<0.01) and that of NRG-1 was increased in the EA group (P<0.05). EA could increase the expression of NRG-1 and reduce the expression of TH and GAP-43 in myocardial tissues in MI mice, which could suppress sympathetic nerve hyperexcitability after infarction to achieve myocardial protection effect.