| Background:In Traditional Chinese Medicine, myocardial ischemia is described as "thoracic obstruction" and "angina pectoris". Due to the excess nutritional intake resulted from remarkably improved living standards, myocardial ischemic disease has become one of the diseases with the highest morbidity and mortality in the world, which poses a serious threat to human health and life. Over the years, a lot of modern medical researches have been carried out to explore the pathogenesis of myocardial ischemia and search for the effective prevention and treatment measures. So far there have been few methods to prevent and treat myocardial ischemic injury except the traditionally-used anticoagulants drugs and stent or bypass surgery, and the incidence and mortality of this disease remain high. As an effective and convenient prevention and treatment method, acupuncture treatment of "thoracic obstruction" and "angina pectoris" was recorded as early as in Huangdi Neijing. A large number of clinical experiences and modern researches have shown that acupuncture has a protective effect against myocardial ischemia, such as alleviating angina and chest tightness symptoms of patients with coronary heart disease, improving left ventricular function and ST-segment of electrocardiogram (ECG) and etc. Therefore, discovering the mechanism of acupuncture protection against myocardial ischemia is of great value for the clinical use of acupuncture, and it will also provide a theoretical basis for acupuncture’s improvement of myocardial ischemia symptoms in patients with coronary heart disease.It is well-known that, during acute myocardial ischemia, over-activated sympathetic activity and cardiac β-adrenergic receptors lead to an overload of intracellular calcium and finally cause myocardial injury. The past researches showed that acupuncture can affect the excitability of the sympathetic nervous system and protect the heart from ischemia injury.β-adrenergic receptor (β-AR) is not only the main target receptor in sympathetic nervous system, but also the most important receptor in the heart. The regulation of heart activity by sympathetic nervous is mainly conducted by the β-AR. Therefore, acupuncture improvement of myocardial ischemic injury may be achieved by affecting the cardiac sympathetic nervous system and thereby desensitizing the responsiveness of β-ARObjective:The model of acute myocardial ischemia was established by ligating the left anterior descending artery (LAD) of rats and forcing mice to swim exhaustively. The aim of the present study was to observe the protective effect of electro-acupuncture (EA) against ischemic myocardium and further investigate the role of β-AR in the mediation of the protective effect of EA treatment, which could provide clinical guidance and theoretical basis for the protection of the heart from injury of ischemia. Method:The first part of the experiment:32male adult Wistar rats weighing235±15g were used in the experiments. The rats were randomly divided into four groups:the Normal Control group (NC), the Model group (Model), the Propranolol group (EAP) and the EA group (EA), with8rats in each group. LAD ligation was performed after anesthesia on rats in the Model group, the EA group and the EAP group. In the EA group, rats were treated with EA applied at bilateral "Neiguan" point (PC6) for30min in3successive days after anesthesia (EA Parameters:intensity of3mA, frequency of20Hz). In EAP group, they were injected with Propranolol intraperitoneally at a dose of10mg/kg after anesthesia, and received EA after15min of injection at bilateral PC6for30min (once a day in3consecutive days). Rats in the NC group received no EA stimulation. The aim of this part of experiment was to verify the protective effect of electro-acupuncture (EA) against ischemic myocardium through observing the ST-segment elevation on the ECG, the score of arrhythmia and the size of myocardial infarct and test whether β-adrenoreceptor mediates the protective effect of EA treatment on myocardium.The second section of experiments:The24C57BL/6mice were randomly divided into three groups:the Control group (Control), the Fatigue group (Fatigue) and the EA group (EA), with8mice in each group. Mice in the Fatigue and EA groups were forced to swim. Mice in the EA group were treated with EA applied at bilateral PC6for30min in7successive days in the self-made mouse sets (EA Parameters:intensity of0.5mA, frequency of2Hz), but mice in the Control group and the fatigue group received no EA stimulation. The24β1/β2-AR double knockout mice were randomly divided into three groups:the Control group (Control), the fatigue group (Fatigue) and the EA group (EA). The same procedures were performed as the experiment on C57BL/6mice. The purpose of this section is to verify the protective effect of electro-acupuncture (EA) against ischemic myocardium and test whether β-adrenoreceptor mediates the protective effect of EA treatment on myocardium.Results:1. Protective effect of EA on PC6against myocardial ischemic injury1.1Effects of EA at Neiguan point in the ST-segment elevation of rats with myocardial ischemia injuryBefore LAD ligation operation, the ST-segment elevation of rats in the Control group, Model group, EA group and EAP group were normal, there were no statistical difference(P>0.05). After3days, no statistical difference was observed in the NC group (P>0.05), but the ST-segment elevation increased, the difference was statistically significant in the Model group (P<0.01). the ST-segment elevation returned to normal level after3days of EA intervention in the EA group and were significantly lower than those of the Model group (P<0.01). However, after3days of intervention, no significant difference was found in the EAP group (P>0.05).1.2Effects of EA at PC6in the score of arrhythmia of rats with myocardial ischemia injuryBefore LAD ligation operation, the score of arrhythmia of rats in the Control group, Model group, EA group and EAP group were normal, there were no statistical difference(P>0.05). After3days, no statistical difference was observed in the NC group (P>0.05), but the score of arrhythmia increased, the difference was statistically significant in the Model group (P<0.01). The score of arrhythmia were significantly lower than those of the Model group after3days of EA intervention in the EA group (P<0.01). However, after3days of intervention, no significant difference was found in the EAP group (P>0.05).1.3Effects of EA at PC6in the myocardial infarct size of rats with myocardial ischemia injuryBefore LAD ligation operation, the myocardial infarct size of rats in the Control group, Model group, EA group and EAP group were normal. After3days, compared to the Control group, the myocardial infarct size increased in the Model group significantly (P<0.01). The myocardial infarct size were significantly lower than those of the Model and EAP group after3days of EA intervention in the EA group (P<0.01).2Discussion on the β-adrenoceptor mediation of the protective effect of EA treatment against myocardium2.1Effects of EA at PC6in C57BL/6mice after exhaustive swimmingMaking indicators of mice in the Control group the baseline, we observed no significant change in terms of the ST-segment amplitude, HR and score of arrhythmia between the first day and the7th day. After exhaustive swimming, compared to the baseline, ST amplitude significantly increased (P<0.01), heart rate decreased (P<0.05), and the score of arrhythmia increased (P<0.05) in both the fatigue group and the EA group. After7days of experiment, no significant change were found in the fatigue group (P>0.05). But all indicators except the heart rate returned to normal level in rats of the EA group after7days of EA stimulation at PC6, and ST amplitude and arrhythmia score were significantly lower than those of the fatigue group (P<0.01and P<0.05respectively).2.2Effects of β-AR mediation of the EA treatment in β1/β2-AR double knockout mice after exhaustive swimmingMaking indicators of the Control group the baseline, we observed no significant difference between the first day and the7th day in ST amplitude, HR and score of arrhythmia. After exhaustive swimming, the ST amplitude and arrhythmia score increased and the heart rate decreased in rats of the fatigue group and the EA group. The differences were statistically significant compared with the baseline (P<0.01). But no significant change was found between the fatigue group and the EA group after7days of intervention (P>0.05). Conclusion:Repetitive Electro-acupuncture at PC6can effectively attenuate ST segment elevation of ECG, myocardial infarct size and arrhythmias and thereby protect cardiac muscles injured by myocardial ischemia. Cardiac β-adrenergic receptors were also involved in the improvement of myocardial ischemia symptoms by Electro-acupuncture at PC6. |
PDF Full Text Request