Research on a novel mechanism for anti-arrhythmogenic effects of electrical vagal nerve stimulation during acute myocardial ischemia

心肌缺血（MI）导致细胞电稳定性紊乱和致命性心律失常的产生。迷走神经刺激被认为有助于抗癫痫作用。在这项研究中，我们证明了一种新的机制，在急性心肌梗死的电迷走神经刺激的抗心律失常的性质。Wistar大鼠在麻醉状态下结扎左冠状动脉（LCA）30 min，同时刺激迷走神经（MI-VS组）和假刺激（MI-SS组）。MI-SS组12只大鼠中有8只在30分钟LCA结扎期间发生室性快速性心律失常（VT）;另一方面，MI-VS组11只大鼠中仅1只发生VT（分别为67%和9%）。阿托品给药可消除迷走神经刺激的抗肿瘤作用。免疫印迹显示，与假手术和假刺激组相比，MI-SS组显示磷酸化连接蛋白43（Cx43）的量显著减少，而MI-VS组仅显示轻微减少（37+/-20% vs 79+/-18%）。免疫组化证实，MI诱导的损失Cx43从细胞间连接被阻止迷走神经刺激。此外，用大鼠原代培养的心肌细胞的研究表明，乙酰胆碱（ACh）有效地防止缺氧诱导的磷酸化Cx43的损失，并改善细胞间通讯的损失，如通过荧光黄染料转移测定所确定的，这支持了体内结果。此外，体外研究还表明，ACh诱导Akt磷酸化，这是抑制渥曼青霉素。提示ACh通过PI 3 K/Akt通路对心肌细胞具有保护作用。总之，迷走神经刺激在急性MI期间发挥抗促炎和抗凋亡作用，因此在改善缺血诱导的电不稳定性和激活细胞存活信号中起关键作用。

Myocardial ischemia (MI) leads to derangements in cellular electrical stability and the generation of lethal arrhythmias. Vagal nerve stimulation has been postulated to contribute to the antifibrillatory effect. In this study, we demonstrate a novel mechanism for the antiarrhythmogenic properties of electrical vagal nerve stimulation during acute MI. Under anesthesia, Wistar rats underwent 30 minutes of left coronary artery (LCA) ligation with vagal stimulation (MI-VS group) and with sham stimulation (MI-SS group). Eight of the 12 rats in the MI-SS group had ventricular tachyarrhythmia (VT) during 30-minute LCA ligation; on the other hand, VT occurred in only 1 of the 11 rats in the MI-VS group (67% versus 9%, respectively). Atropine administration abolished the antiarrhythmogenic effect of vagal stimulation. Immunoblotting revealed that the MI-SS group showed a marked reduction in the amount of phosphorylated connexin43 (Cx43), whereas the MI-VS group showed only a slight reduction compared with the sham operation and sham stimulation group (37+/-20% versus 79+/-18%). Immunohistochemistry confirmed that the MI-induced loss of Cx43 from intercellular junctions was prevented by vagal stimulation. In addition, studies with rat primary-cultured cardiomyocytes demonstrated that acetylcholine (ACh) effectively prevented the hypoxia-induced loss of phosphorylated Cx43 and ameliorated the loss of cell-to-cell communication as determined by Lucifer Yellow dye transfer assay, which supports the in vivo results. Furthermore, in-vitro studies also revealed that ACh induced Akt phosphorylation, which was inhibited by wortmannin. These results suggest that ACh protects cardiomyocytes through the PI3K/Akt pathway. In conclusion, vagal nerve stimulation exerts both anti-arrhythmogenic and anti-apoptotic effects during acute MI and thus plays a critical role in improving ischemia-induced electrical instability and in activating cell-survival signals.