Effects of postconditioning with electric vagal stimulation on myocardial ischemia-reperfusion injury in rats

Objective To investigate the effects of postconditioning with electric vagal stimulation on myocardial ischemia-reperfusion (I/R) injury in rats.Methods Sixty male SD rats weighing 250-350 g were randomly divided into 3 groups (n ＝ 20 each):group sham operation (group S); group myocardial I/R (group I/R) and group electric vagal stimulation postconditioning (group POES).Myocardial I/R was induced by occlusion of left anterior descending branch of coronary artery for 30 min followed by 120 min reperfusion in groups I/R and POES.In group POES right cervical vagus nerve trunk was stimulated for 30 min with continuous electric rectangular pulses (2 ms,10 Hz) starting from 15 min of myocardial ischemia.The voltage of the pulses was adjusted to decrease HR by 10％ of the baseline HR before stimulation.MAP,HR and RPP (MAP× HR) were recorded before (baseline) and at 1 and 10 min of ischemia and 30,60 and 120 min of reperfusion.Arterial blood samples were collected from 10 rats in each group at 120 min of reperfusion for determination of serum concentrations of cTnI,CK-MB,TNF-a,high mobility group box 1 protein (HMGB1),ICAM-1,IL-1,IL-6 and IL-10 (by ELISA).The animals were then sacrificed and myocardial infarct size was measured by Evans blue and TTC staining.Another 10 rats were sacrificed at 120 min of reperfusion for determination of myocardial contents of TNF-α,HMGB1,ICAM-1,IL-1,IL-6 and IL-10 (by ELISA).Results I/R induced myocardial infarct,significantly increased serum concentrations of cTnI,CK-MB,TNF-α,HMGB1,ICAM-1,IL-1 and IL-6 and significantly increased myocardial contents of TNF-α,HMGB1,ICAM-1,IL-1,IL-6 and IL-10 in both ischemic and non-ischemic regions in group I/R as compared with group S.Electric vagal stimulation significantly decreased myocardial infarct size and serum concentrations of cTnI,CK-MB,TNF-α,HMGB1,1CAM-1,IL-1 and IL-6 in group POES compared with group I/R.Myocardial contents of TNF-α,HMGB1,ICAM-1,IL-1 and IL-6 were significantly decreased while myocardial IL-10 content was increased in both ischemic and non-isehemic regions in groups POES compared with group I/R.Conclusion Postconditioning with electric vagal stimulation can attenuate myocardial I/R injury by inhibiting inflammatory response in rats. Key words: Electric stimulation; Vagus nerve; Myocardial reperfusion injury