| Objective: This study aims to investigate the therapeutic effect of ta-VNS and its potential mechanism by giving intermitnent ta-VNS in the dog models during chronic MI phase.Methods: 14 male dogs were randomized into two groups,the one was control group(MI+sham ta-VNS,n=7),the other one was ta-VNS group(MI+ta-VNS,n=7).Dynamic ECG recording,electrophysiological measurements,neural recording,catecholamine concentration and histological studies were conducted subsequently.Results: Electrophysiological results showed that endocardial effective refractory period(ERP),epicardial ERP in peri-infarction and non-infarction area of ta-VNS group enlarged in contrast to that in control group(P < 0.05).In contrast to control group,ta-VNS significantly increased HF power and reduced LF power(P<0.05).In the ta-VNS group,with the progress of reduced cardiac sympathetic activities and augmented cardiac parasympathetic activities,catecholamine concentration of heart tissue declined in the peripheral infarction area and RV(P<0.05);TH-positive neurons decreased in inferior cardiac sympathetic nerve and ChAT-positive neurons increased in the cervical vagus nerve(P<0.05).In the peri-infarct and non-infarct areas,NFH in the ta-VNS group was significantly higher than that in the control group(P<0.05),P75 NTR and TrKA in the ta-VNS group were significantly reduced than that in the control group(all P<0.05),and ADRB1 in the ta-VNS group was significantly lower than that in the control group(all P<0.05).Conclusion: ta-VNS effectively suppressed the VAs burden in the chronic MI phase by rebalancing the autonomic tone and enhancing the ventricular electrophysiological properties.Its potential mechanisms were associated with rebalanced extracardiac intrathoracic autonomic activities,reduced excessive cardiac sympatheticdenervation and attenuated the heterogeneities of cardiac efferent nerve receptors distribution. |
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