Glutamatergic neurons in lateral hypothalamus play a vital role in acupuncture preconditioning to alleviate MIRI.

Myocardial ischemia-reperfusion injury (MIRI) has high morbidity and mortality worldwide. Increasing evidence has shown that electroacupuncture (EA) plays a critical role in alleviating MIRI. The aim of this study is to investigate whether glutamatergic neurons in the lateral hypothalamus (LH) have vital effect on MIRI as well as the underlying mechanism during the EA pretreatment. The MIRI model was established by ligating the left anterior descending (LAD) coronary artery for 30 min followed by reperfusion for 2 h. Chemogenetics, electrocardiogram (ECG) recording, ELISA, multichannel physiology recording, and immunofluorescence staining methods were combined to demonstrate that firing frequencies of neurons in the LH and expression of c-Fos decreased by EA pretreatment. Meanwhile, EA preconditioning significantly reduced the percentage of infarct size and the levels of cardiac troponin I (cTnI) and creatine kinase isoenzymes (CK-MB) were similar to inhibition of glutamatergic neurons in LH, also attenuated morphology of myocardial tissue was induced by MIRI. However, activation of glutamatergic neurons in LH weakened the above effects of EA pretreatment.NEW & NOTEWORTHY This study demonstrates that EA preconditioning can attenuate myocardial injury for MIRI, which is similar to inhibition of glutamatergic neurons in LH. However, chemical activation of glutamatergic neurons in LH attenuates the protective effect of EA pretreatment. These findings help better understand the mechanisms of EA to regulate cardiac function.

[Effects of electroacupuncture pretreatment on GABAA receptor of fastigial nucleus and sympathetic nerve activity in rats with myocardial ischemia reperfusion injury].

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.

Mechanisms of Electroacupuncture Pretreatment in Alleviating Myocardial Ischemia Reperfusion Injury: Interactions between the Cerebellar Fastigial Nucleus and Lateral Hypothalamic Area.

Background: Myocardial ischemia reperfusion injury (MIRI) is an important mechanism of post-myocardial infarction injury and a main cause of death in patients with ischemic heart disease. Electroacupuncture (EA) pretreatment is effective for the prevention and treatment of MIRI, but mechanisms mediating the effects of cardiovascular disease EA treatments remain unclear. Objectives: To determine whether the lateral hypothalamus (LHA) and the cerebellar fastigial nucleus (FN) are involved in the protective effects of EA stimulation on MIRI. Methods: EA pretreatment was performed for 7 days before the establishment of the MIRI model. ST-segment changes on electrocardiograms were recorded and the Curtis-Walker arrhythmia score was used to evaluate changes in reperfusion injury. Hematoxylin-eosin staining was applied to evaluate the pathological and morphological changes in myocardial tissue. c-fos expression in the LHA and FN was determined by immunofluorescence staining. Glutamic (Glu) and γ-Aminobutyric acid (GABA) levels were measured using a high-performance liquid chromatography-electrochemical method. Results: EA pretreatment reduced ST-segment elevation, arrhythmia scores, and morphological changes in MIRI myocardial cells in rats, and decreased the c-fos protein expression in LHA/FN nuclei. MIRI was associated with an imbalance between GABA and Glu levels, whereas EA pretreatment increased GABA levels and decreased Glu levels in the LHA/FN. Conclusion: FN and LHA are involved in the EA-mediated attenuation of MIRI. Pretreatment with EA plays a protective role in the myocardium by regulating Glu and GABA release in the LHA and FN.