Experimental Study of the Effect of Autonomic Nervous System on the Transmural Dispersion of Ventricular Repolarization under Acute Myocardial Ischemia in Vivo

Summary: The effect of the autonomic nerves on the transmural dispersion of ventricular repolarization (TDR) under acute myocardial ischemia in intact canine was investigated. Using the monophasic action potential (MAP) recording technique, MAPs of the epicardium (Epi), midmyocardium (Mid) and endocardium (Endo) were recorded simultaneously by specially designed plunge-needle electrodes at the left ventricular free wall under acute myocardial ischemia in 12 open-chest dogs. MAPD 90 and TDR among three myocardial layers as well as the incidence of the early afterdepolarization (EAD) before autonomic nervous stimulation and during autonomic nervous stimulation were compared. It was found that 10 min after acute myocardial ischemia, TDR was increased from 55±8 ms to 86±15 ms during sympathetic stimulation (P<0.01). The TDR (53±9 ms) during parasympathetic stimulation was not significantly different from that of the control (55±8 ms) (P>0.05). The EAD was elicited in the Mid of 2 dogs (16 %) 10 min after acute myocardial ischemia, but the EAD were elicited in the Mid of 7 dogs (58 %) during sympathetic stimulation (P<0.01). It was concluded that: (1) Sympathetic stimulation can increase the transmural dispersion of repolari-zation and induce early afterdepolarizations in the Mid under acute myocardial ischemia, which provide the opportunity for the ventricular arrhythmia developing; (2) Parasympathetic stimulation has no significant effect on the transmural dispersion of repolarization under myocardial ischemia.

Effect of electroacupuncture "Shenmen" on the expression of cAMP and cGMP in the myocardium, hippocampus and serum of rats with acute myocardial ischemia

Objective:Discussion on the protectiion of electroacupuncture"Shenmen"on heart and brain injury induced by acute myocardial ischemia in rats from the perspective of the expression of cyclic adenosine monophosphate(cAMP)and cyclic guanosine monophosphate(cGMP).Methods:Thirty male SD rats were randomly divided into normal group,model group,and electroacupuncture group.The electrocardiogram was recorded by the Powerlab 8-lead physiological recording system.The left anterior descending coronary artery was ligated to replicate the rat myocardial ischemia model.The acupuncture group was treated with electroacupuncture on the second day after the model was replicated.After the last electroacupuncture treatment,rat myocardium,hippocampus tissue and abdominal aortic blood were collected,and enzyme-linked immunosorbent assay was used to detect the levels of cAMP and cGMP in myocardium,hippocampus tissue and serum content.Results:Compared with the normal group,the cAMP content in the myocardial tissue of the model group was significantly increased,and the cAMP content in the hippocampus tissue and serum was significantly reduced;compared with the model group,the cAMP content in the myocardial tissue of the electroacupuncture group was decreased,and the hippocampus tissue Compared with the normal group,the content of cGMP in the myocardial tissue and serum of the model group increased,and the content of cGMP in the hippocampus decreased.Compared with the model group,the content of cGMP in the hippocampus of the electroacupuncture group was increased.The cGMP content increased,the serum cGMP content was significantly reduced,and the difference in the cGMP content in myocardial tissue was not statistically significant.Conclusion:Electroacupuncture at"Shenmen"acupoint can significantly improve the expression of cAMP,cGMP and myocardial cAMP in the serum and hippocampus of model rats with acute myocardial ischemia-induced heart and brain injury,but has a lower effect on myocardial cGMP content.

Effects of electroacupuncture of acupoints of the neiguan and ximen on ischemic myocardium energy metabolism with acute myocardial ischemia rats

Objective:To observe the effect of Electroacupuncture of Acupoints of the Neiguan(PC6)and Ximen(PC4)on its myocardial energy metabolism with acute myocardial ischemia rats caused by coronary artery ligation.Methods:Forty standard Spargue-Dawely(SD)rats were divided into four groups randomly,namely,group of Neiguan,group of Ximen,model group,sham group.The group of rats of myocardial ischemia were induced by coronary ligation,and the model rat of acute myocardial ischemia was prepared.The sham group had no ligation of the needle.After anesthesia was awakened,acupuncture was applied bilateral at Neiguan and Ximen of the group of Neiguan and Ximen,once a day at a fixed time for 14 days.The rats of model group and the sham group were not given acupunctured,but use the samely methods of Neiguan and Ximen groups to grap the rats at the same time everyday.After 14 days the experiment was over,observed the pathological changes of myocardial tissue by HE staining,detected the levels of free fatty acid(FFA),adenosine triphosphate(ATP)content,and the activities of Na^(+)-K^(+)-ATPase according to the reagents´demand.Results:Pathological results showed that acupuncuted at Neiguan and Ximen could improve the ischemic cardiomyocyte injury.Compared with the sham group,the levels of FFA in model group were increased(p<0.01),the levels of ATP,the activities of Na^(+)-K^(+)-ATPase were all decreased(p<0.01);Compared with the model group,the levels of FFA were decreased(p<0.05,p<0.01),the levels of ATP,the activities of Na^(+)-K^(+)-ATPase were improved.Conclusion:Acupuncturing at the Pericardium Meridian can alleviate the cell injury by myocardial ischemia,and also can improve the myocardial energetic metabolism in acute myocardial ischemia.

Hawthorn Leaves Flavonoids Decreases Inflammation Related to Acute Myocardial Ischemia/Reperfusion in Anesthetized Dogs

Objective： To investigate the effects and mechanisms of hawthorn leaves flavonoids （HLF） on acute myocardial ischemiaJreperfusion in anesthetized dogs. Methods： The acute ischemia models were prepared by ligating left anterior descending （LAD） artery for 60 min. Qualified 15 male dogs were randomly divided into 3 groups with 5 in each group： blank control （treated with normal saline 3 mL/kg） group, HLF low dosage （5 mg/kg） group and high dosage （10 mg/kg） group, with an once injection through a femoral vein 5 min before reperfusion. Epicardial electrocardiogram was adopted to measure the scope and degree of myocardial ischemia. Simultaneously, neutrophil infiltration in infarct （Inf） and remote site （RS） of myocardial tissue was measured by myeloperoxidase （MPO） activity assay. The serum interleukin-1 （IL-1） and tumor necrosis factor~ （TNF-~） content were quantified by radioimmuno-assay. Furthermore, expression of G protein-coupled receptor kinase 2 （GRK2） and nuclear factor K B （NF- K B） in Inf and RS tissue were detected by Western blotting technique. Results： Ischemia and reperfusion increased the MPO activity and IL-1 and TNF-~ content. HLF （10 and 5 mg/kg） could significantly decrease the degree and scope of myocardial ischemia; markedly inhibit the increase of MPO activity, and IL-1 and TNF-o~ content induced by myocardial ischemia/infarction. Furthermore, HLF increased GRK2 expression and inhibited NF- K B expression in Inf tissue. Conclusion： HLF could improve the situation of acute myocardial ischemia and inhibit the inflammation in anesthetized dogs, which might be due to its increasing effect on the GRK2 and NF- K B expressions.

Cardio-protective Effects of Corocalm (疏冠胶囊) on Acute Myocardial Ischemia/Reperfusion Injury in Rats

Objective： To investigate the cardio-protective effects of Corocalm （疏冠胶囊） on acute myocardial ischemia in rats, and to explore its possible therapeutic mechanisms. Methods： The acute ischemic model was prepared by ligating the left anterior descending （LAD） coronary artery in rats. The animals were divided into 6 groups, 8 in each group. The sham operated group underwent heart exposure without ligation and were treated with normal saline 3 ml/kg, while the other 5 groups, the model groups, consisted of acceptable acute ischemic model rats and were also treated with normal saline, with the Guanxin Capsule （ 冠心胶囊, GXC） group treated with refined GXC, 600 mg/kg, the low and high dose Corocalm groups treated with 85 mg/kg and 340 mg/kg of Corocalm respectively, and the Diltiazem group, treated with Diltiazem 5 mg/kg, with all the tested drugs prepared with normal saline into equal volume （ 3 ml/kg） and administrated once via duodenum 10 rain before ligation. Myocardial infarction area was determined by the quantitative histological assay with nitroblue tetrazolium （N-BT） stain. And the levels of creatine phosphokinase （CK）, lactate dehydrogenase （LDH）, malondialdehyde （MDA） content, and the activity of superoxide dismutase （SOD） in serum were measured by biochemical assay and spectrophotometry respectively. Besides, the blood viscosity in another 50 rats was determined, who received for 7 successive days oral administration with different concentration of Corocalm or aspirin. Results： It showed that low and high dose Corocalm could significantly reduce the infarction area, inhibit the increase of serum OK, LDH activity and MDA content, and enhance the SOD activity after ischemia/reperfusion. The whole blood viscosity at different shear rates in rats treated with high dose Corocalm was significantly lower than those treated with normal saline （P 0.05）. Conclusion： Corocalm has favourable protective effects on heart in ischemic condition, the effect of which might be through its actions in inhibiting CK and LDH activity, scavenging oxygen free radicals, and lowering blood viscosity.

Gualou-Xiebai-Banxia decoction protects against type Ⅱ diabetes with acute myocardial ischemia by attenuating oxidative stress and apoptosis via PI3K/Akt/eNOS signaling

Gualou-Xiebai-Banxia decoction has a long history of medical use for treating cardiovascular diseases in China.In this study,we investigated the protective effect and underlying mechanisms GXB in typeⅡdiabetes with acute myocardial ischemia(T2DM-AMI)rats.We hypothesized that GXB may display its protective effect on T2DM-AMI by reducing endothelial progenitor cells(EPCs)apoptosis via activating PI3K(phosphatidyl inositol 3-kinase)/Akt(serine/threonine protein kinase B)/e NOS(endothelial nitric oxide synthase)signaling.Rats were challenged with a high-fat diet and intraperitoneal injection of streptozotocin to induce a model of typeⅡdiabetes mellitus(T2DM)and coronary ligation to induce acute myocardial infarction(AMI).Changes in metabolites were assessed via enzyme-linked immunoassay and biochemical examination.The number and apoptosis rate of EPCs in peripheral blood were detected by flow cytometry.Target m RNAs and proteins in EPCs were analyzed by RT-PCR and Western blot analysis.The results demonstrated that GXB treatment decreased T2DM-AMI-associated changes in plasma fasting blood glucose,muscular enzymes,and blood lipids,and reduced oxidative stress.Furthermore,EPC apoptosis was increased in T2DM-AMI rats and was associated with decreased m RNA and protein levels of PI3K,Akt,and eNOS compared to the controls.Conversely,T2DM-AMI rats treated with GXB exhibited more circulating EPCs and downregulated levels of cell apoptosis,combined with increased m RNA and protein levels of PI3 K,Akt,and eNOS compared to those of untreated T2DM-AMI rats.Our study showed that GXB treatment mitigated EPC apoptosis and promoted PI3K/Akt/eNOS signaling in T2DM-AMI rats.

Influence of Acupuncture on Microcirculation Perfusion of Pericardium Meridian and Heart in Acute Myocardial Ischemia Model Rats

Objective: To observe the influence of acupuncture on microcirculation perfusion of the pericardium meridian and heart in acute myocardial ischemia(AMI) rats and evaluate whether acupuncture can simultaneously affect the meridians and corresponding viscera. Additionally, acupoints at different meridians were compared and whether they exert the same effects was discussed. Methods: Totally 32 Sprague-Dawley rats were subjected to left anterior descending(LAD) ligation to develop an AMI model.Rats were divided into 4 groups, including AMI, acupuncture Neiguan(PC 6), Lieque(LU 7) and Qiansanli(LI 10) groups(n=8). Eight rats received only thoracotomy(sham-operated group). The rats in the acupuncture groups received manual acupuncture at PC 6, LU 7 and LI 10 acupoints for 15 min, respectively. The microcirculation perfusion of pericardium meridian and heart was monitored by laser speckle perfusion imager(LSPI) before, during and after acupuncture manipulation for 15 min. Subsequently, the perfusion unit(PU)was calculated and analyzed by PSI System. Results: After LAD, compared to pre-acupuncture stage, the heart microcirculation perfusion(HMP) in the AMI group decreased continuously at during-acupuncture(P>0.05) and post-acupuncture stages(P<0.05), and the pericardium meridian microcirculation perfusion(PMP) showed no significant differences at 3 stages(P>0.05). Compared to pre-acupuncture stage, the PMP and HMP in PC 6 group significantly increased during acupuncture manipulation(both P<0.05), and PMP decreased obviously after acupuncture(P<0.05). The PMP in the LU 7 and LI 10 groups were slightly elevated(both P>0.05);however, they were significantly reduced after acupuncture manipulation(both P<0.05). Additionally, HMP of LI 10 group was decreased significantly during acupuncture, especially compared to pre-acupuncture stage(P<0.05). Conclusions: Acupuncture at PC 6 obviously increased the PMP and HMP in AMI rats, and the effects were superior to at LU 7 and LI 10 acupoints. It was further confirmed that acupuncture promoted qi and blood circulation, indicating that acupoint specificity exists and features a meridian-propagated effect.

Effects of Corocalm (Shuguan Capsule,疏冠胶囊) on Acute Myocardial Ischemia in Anesthetized Dogs

Objective： To investigate the effects of Corocalm （Shuguan Capsule, 疏冠胶囊） on acute myocardial ischemia in anesthetized dogs and its possible therapeutic mechanism. Methods： The acute ischemia model was established by ligating the left anterior descending （LAD） artery. Twenty- five dogs were randomly divided into 5 groups （5 dogs in each group）： the control group （treated with normal saline 3 mL/kg）, the refined Guanxin Capsule group （精制冠心胶囊, GXC 200 mg/kg）, high and low dose Corocalm groups （48.5 mg/kg for low dose group and 194.0 mg/kg for high dose group） and the Diltiazem group （5 mg/kg）. The animals were treated via a single duodenal administration after the model was established. The experiments used epicardial electrocardiogram （EECG） to measure the scope and degree of myocardial ischemia. Simultaneously, the coronary blood flow （CBF） and serum activity levels of creatine phosphokinase （CK） and lactate dehydrogenase （LDH） were measured by electromagnetic flow meter and automatic biochemical analyzer respectively. The plasma endothelin （ET） content was quantified by radioimmunoassay. Results： Corocalm （48.5 mg/kg and 194.0 mg/kg） significantly decreased the degree and scope of myocardial ischemia, reduced the infarct area, markedly increased the CBF, and inhibited the increase of CK and LDH activities and ET levels induced by myocardial ischemia/infarction. Conclusion： Corocalm could improve the state of acute myocardial ischemia and infarction in dogs. The mechanism of action might be correlated to increasing CBF, inhibiting CK and LDH activities and preventing ET release.

Metabolic risk factors associated with sudden cardiac death(SCD)during acute myocardial ischemia

Sudden cardiac death(SCD)is the leading cause of death worldwide.Myocardial ischemia(MI)is the most common underlying causal disorder for SCD.Metabolic risks leading to SCD during acute MI are still not fully understood.Here,using tissue metabolomics,we aimed to investigate myocardial metabolic alterations relevant to SCD events in an acute MI rat model induced by coronary artery ligation(CAL).Thirty-four rats were successfully performed CAL,of which 13 developed lethal ventricular tachyarrhythmia(LVTA)-SCD and 7 developed severe atrioventricular block(AB)-SCD.Fourteen rats that survived within 70 min after the ligation were served as peer controls.The partial least squares-discriminant analysis plots demonstrated clear separations between the SCD rats and controls,indicating obvious differences in myocardial metabolome between these rats.The levels of isoleucine,lactate,glutamate choline,phosphorylcholine,taurine and asparagine in ischemic myocardia were positively associated with LVTA-SCD events;in contrast,the levels of alanine,urea,phenylalanine,linoleic acid,elaidic acid and stearic acid were inversely correlated with LVTA-SCD events.The levels of glutamate and urea were positively and negatively relevant to AB-SCD events,respectively.The dangerous metabolites indicated that lower levels of energy substrates,severe hypoxia,the inhibition of transamination and hyper sympathetic excitement and reactive oxygen species in myocardia were vulnerable to SCD during acute MI.The results suggest fatal metabolic alterations correlated with SCD events during acute MI,which could offer novel clues for the prevention or treatment of acute MI-related SCD.

Electroacupuncture modulates the activity of the hippocampus-nucleus tractus solitarius-vagus nerve pathway to reduce myocardial ischemic injury

The hippocampus is involved in the regulation of the autonomic nervous system,together with the hypothalamus and brainstem nuclei,such as the paraventricular nucleus and nucleus tractus solitarius.The vagus nerve-nucleus tractus solitarius pathway has an important role in cardiovascular reflex regulation.Myocardial ischemia has been shown to cause changes in the autonomic nervous system,affecting the dynamic equilibrium of the sympathetic and vagal nerves.However,it remains poorly understood how the hippocampus communicates with brainstem nuclei to regulate the autonomic nervous system and alleviate myocardial ischemic tissue damage.A rat model of acute myocardial ischemia（AMI） was made by ligating the left anterior descending branch of the coronary artery.Three days before ischemia,the hippocampal CA1 region was damaged.Then,3 days after ischemia,electroacupuncture（EA） at Shenmen（HT7）-Tongli（HT5） was performed（continuous wave,1 m A,2 Hz,duration of 30 minutes）.Cluster analysis of firing patterns showed that one type of neuron was found in rats in the sham and AMI groups.Three types of neurons were observed in the AMI ＋ EA group.Six types of neurons were found in the AMI ＋ EA ＋ Lesion group.Correlation analysis showed that the frequency of vagus nerve discharge in each group was negatively correlated with heart rate（HR）（P 〈 0.05,r =-0.424）,and positively correlated with mean arterial pressure（MAP）（P 〈 0.05,r = 0.40987） and the rate-pressure product（RPP）（P 〈 0.05,r = 0.4252）.The total frequency of the nucleus tractus solitarius discharge in each group was positively correlated with vagus nerve discharge（P 〈 0.01,r = 0.7021）,but not with hemodynamic index（HR： P 〉 0.05,r =-0.03263; MAP： P 〉 0.05,r =-0.08993; RPP： P 〉 0.05,r =-0.03263）.Some neurons（Neuron C） were negatively correlated with vagus nerve discharge,HR,MAP and RPP in the AMI ＋ EA group（vagus nerve discharge： P 〈 0.05,r =-0.87749; HR： P 〈 0.01,r =-0.91902; MAP： P 〈 0.05,r =-0.85691; RPP： P 〈 0.01,r =-0.91902）.Some neurons（Neurons C,D and E） were positively correlated with vagus nerve discharge,HR,MAP and RPP in the AMI ＋ EA ＋ Lesion group（vagus nerve discharge： P 〈 0.01,r = 0.8905,P 〈 0.01,r = 0.9725,P 〈 0.01,r = 0.9054; HR： P 〈 0.01,r = 0.9347,P 〈 0.01,r = 0.9089,P 〈 0.05,r = 0.8247; MAP： P 〈 0.05,r = 0.8474,P 〈 0.01,r = 0.9691,P 〈 0.01,r = 0.9027; RPP： P 〈 0.05,r = 0.8637,P 〈 0.01,r = 0.9407,P 〈 0.01,r = 0.9027）.These findings show that the hippocampus-nucleus tractus solitarius-vagus nerve pathway is involved in the cardioprotective effect of EA at the heart meridian.Some interneurons in the nucleus tractus solitarius may play a particularly important role in the cardiomodulatory process.

Rapid expression of vascular endothelial growth factor in early acutemyocardial ischemia in rats

Objective To study the expression of vascular endothelial growth factor(VEGF) in different parts of heart during early acute myocardial ischemia Methods The expression of VEGF in control and study group in rats was performed with the Strept Avidin Biotin Peroxidase Complex (SABC) method Results A rapid expression of VEGF in ischemic areas was observed 1 hour after the ligation of rat left anterior descending (LAD) coronary artery, and in peri ischemic and non ischemic areas 3 hours after ischemia The grade of expression of VEGF increased with the continuation of myocardial ischemia, the positive myocytes of SABC VEGF staining mainly localized in peri ischemic areas 5 hours after ischemia No expression of VEGF in control group was found Conclusion The expression of VEGF may be up regulated in rapid and continuous manner with characteristic spatial and temporal kinetic during early acute myocardial ischemia

Effect of Electroacupuncture on Reperfusion Ventricular Arrhythmia in Rat

Protective effect and mechanism of electroacupuncture （EA） on acute reperfusion ventricular arrhthmia was investigated. Ventricular arrhythmia was induced by occlusion of the proximal left anterior descend （LAD） branch of coronary artery for 5 min and followed with 15 min reperfusion . EA on acupoint ＂Neiguan＂, ＂Jianshi＂ was performed at 30 min before ligation and continued another 5 min during ischemia. Isoprenaline （20, 30 and 50 μg/kg） or atropine （1 mg/ kg） was intravenously injected at 5min before ischemia. The results showed that EA significantly decreased the incidence of ischemia/reperfusion （I/R） induced ventricular tachycardia （VT）, ventricular fibrillation （VF） and mortality as compared to I/R group. Atropine partially suppressed the EA＇s effect of antiarrhythmia; Isoprenaline increased the incidence and severity of reperfusion arrhythmia, which was inhibited by EA, but this inhibition of EA was blocked with increasing dose of isoprenaline. The results indicated that EA treatment could prevent the occurrence of reperfusion ventricular arrhythmia in rats with myocardial ischemia, and its mechanism might be related to the regulation of EA on the β-adrenoceptors and M-cholinergic receptor activation in myocardium.

Effect of Yuxintong（愈心痛）Capsule on SerumCreatine Phosphokinase Activity and Plasma Endothelin Concentrati

The protective effect of the traditional Chinese compound medicine Yuxingtong (YXT) in cap-sule form on the experimental acute myocardial ischemia formation has been studied in dogs. The plasma en-dotlielin concentration and serum creatine phosphokinase activity were measured after coronary occlusion indifferent medication groups and compared with the saline control group. Results showed that YXT could signifi-cantly lowered the plasma endothelin concentration and the serum creatine phosphokinase activity, it sug-gested that both YXT and diltiazem have the similar protective effect on acute myocardial ischemia and necro-sis in dogs.