Objective: To observe the effects of electroacupuncture (EA) pretreatment on cardiac function, sympathetic nerve activity, indexes of myocardial injury and GABAA receptor in fastigial nucleus in rats with myocardial ischemia reperfusion injury (MIRI), and to explore the neuroregulatory mechanism of EA pretreatment in improving MIRI.
Methods: A total of 60 male SD rats were randomly divided into a sham operation group, a model group, an EA group, an agonist group and an agonist+EA group, 12 rats in each group. The MIRI model was established by ligation of the left anterior descending coronary artery. EA was applied at bilateral "Shenmen" (HT 7) and "Tongli" (HT 5) in the EA group and the agonist+EA group, with continuous wave, in frequency of 2 Hz and intensity of 1 mA, 30 min each time, once a day for 7 consecutive days. After intervention, the MIRI model was established. In the agonist group, the muscone (agonist of GABAA receptor, 1 g/L) was injected in fastigial nucleus for 7 consecutive days before modeling, 150 μL each time, once a day. In the agonist+EA group, the muscone was injected in fastigial nucleus 30 min before EA intervention. The data of electrocardiogram was collected by PowerLab standard Ⅱ lead, and ST segment displacement and heart rate variability (HRV) were analyzed; the serum levels of norepinephrine (NE), creatine kinase isoenzyme MB (CK-MB) and cardiac troponin I (cTnI) were detected by ELISA; the myocardial infarction area was measured by TTC staining; the morphology of myocardial tissue was observed by HE staining; the positive expression and mRNA expression of GABAA receptor in fastigial nucleus were detected by immunohistochemistry and real-time PCR.
Results: Compared with the sham operation group, in the model group, ST segment displacement and ratio of low frequency to high frequency (LF/HF) of HRV were increased (P<0.01), HRV frequency domain analysis showed enhanced sympathetic nerve excitability, the serum levels of NE, CK-MB and cTnI were increased (P<0.01), the percentage of myocardial infarction area was increased (P<0.01), myocardial fiber was broken and interstitial edema was serious, the positive expression and mRNA expression of GABAA receptor in fastigial nucleus were increased (P<0.01). Compared with the model group, in the EA group, ST segment displacement and LF/HF ratio were decreased (P<0.01), HRV frequency domain analysis showed reduced sympathetic nerve excitability, the serum levels of NE, CK-MB and cTnI were decreased (P<0.01), the percentage of myocardial infarction area was decreased (P<0.01), myocardial fiber breakage and interstitial edema were lightened, the positive expression and mRNA expression of GABAA receptor in fastigial nucleus were decreased (P<0.01). Compared with the EA group, in the agonist group and the agonist+EA group, ST segment displacement and LF/HF ratio were increased (P<0.01), HRV frequency domain analysis showed enhanced sympathetic nerve excitability, the serum levels of NE, CK-MB and cTnI were increased (P<0.01), the percentage of myocardial infarction area was increased (P<0.01), myocardial fiber breakage and interstitial edema were aggravated, the positive expression and mRNA expression of GABAA receptor in fastigial nucleus were increased (P<0.01).
Conclusion: EA pretreatment can improve the myocardial injury in MIRI rats, and its mechanism may be related to the inhibition of GABAA receptor expression in fastigial nucleus, thereby down-regulating the excitability of sympathetic nerve.
目的：观察电针预处理对心肌缺血再灌注损伤（MIRI）大鼠心功能、交感神经活动及心肌损伤相关指标、小脑顶核（FN）γ-氨基丁酸A受体（GABAA受体）的影响，探讨电针预处理改善MIRI的神经调节机制。方法：将60只雄性SD大鼠随机分为假手术组、模型组、电针组、激动剂组、激动剂＋电针组，每组12只。采用冠状动脉左前降支结扎法制备MIRI模型。电针组和激动剂+电针组于双侧“神门”“通里”行电针干预，连续波，频率2 Hz，电流强度1 mA，每次30 min，每天1次，连续干预7 d后制备模型；激动剂组于造模前连续7 d 于FN注射GABAA受体激动剂麝香酮（1 g/L），每次150 μL，每天1次；激动剂+电针组在每次电针前30 min于FN注射麝香酮。通过PowerLab标准Ⅱ导联采集各组大鼠心电图数据，分析ST段位移值及心率变异性（HRV）；ELISA法检测血清去甲肾上腺素（NE）、肌酸激酶同工酶MB（CK-MB）和心肌肌钙蛋白I（cTnI）含量；TTC染色法检测大鼠心肌梗死面积；HE染色法观察大鼠心肌组织形态；免疫组化法和实时荧光定量PCR法检测大鼠FN GABAA受体阳性表达及mRNA表达。结果：与假手术组比较，模型组大鼠ST段位移值、HRV低频和高频比值（LF/HF比值）升高（P<0.01），HRV频域分析表明交感神经兴奋性增强，血清NE、CK-MB、cTnI含量升高（P<0.01），心肌梗死面积占比增加（P<0.01），心肌纤维断裂、细胞间质水肿严重，FN GABAA受体阳性表达及mRNA表达升高（P<0.01）；与模型组比较，电针组大鼠ST段位移值、LF/HF比值降低（P<0.01），HRV频域分析表明交感神经兴奋性降低，血清NE、CK-MB、cTnI含量降低（P<0.01），心肌梗死面积占比减少（P<0.01），心肌纤维断裂及细胞间质水肿减轻，FN GABAA受体阳性表达及mRNA表达降低（P<0.01）；与电针组比较，激动剂组及激动剂＋电针组ST段位移值、LF/HF比值升高（P<0.01），HRV频域分析表明交感神经兴奋性增强，血清NE、CK-MB、cTnI含量升高（P<0.01），心肌梗死面积占比增加（P<0.01），心肌纤维断裂、细胞间质水肿加重，FN GABAA受体阳性表达及mRNA表达升高（P<0.01）。结论：电针预处理可改善MIRI大鼠心肌损伤，其机制与抑制FN GABAA受体表达从而改善交感神经兴奋性有关。.
Keywords: GABAA receptor; electroacupuncture pretreatment; fastigial nucleus; myocardial ischemia reperfusion injury; neural mechanism.