| Objective: Learn how to make a rat model of myocardial infarction.To establish a method for the determination of the electrical activity of the cervical sympathetic nerve and record the epicardial monophasic action potential by single electrode in rats.To explore the effect of cervical sympathetic nerve on ventricular arrhythmia after myocardial infarction in rats and To promote the sympathetic nerve sprouting in the heart of normal rats,whether it will make ventricular arrhythmia susceptibility or not.Methods: Under anesthesia,tracheal intubation,ligation the anterior descending coronary artery,resulting in acute myocardial ischemia in rats,to build myocardial infarction model.The anterior cervical skin was incised and the cervical sympathetic nerve was found,then to peel off the sympathetic nerve sheath.Keeping sympathetic and peripheral tissue separation.Determination of the electrical activity of the cervical sympathetic nerve by means of an electrophysiological apparatus.(1)6-hydroxydopamine(6-OHDA)denervation model:Rats were randomly divided into sham operation group(sham+Vc),sham operation control group(sham+6-OHDA),myocardial infarction group(AMI+Vc)and myocardial infarction control group(AMI +6-OHDA).Sham+6-OHDA group and AMI+6-OHDA group were injected with 6-hydroxydopamine(6-OHDA)for 3 days to remove the sympathetic nerve,then Sham+Vc and AMI+Vc were given the same dose of 0.2% Vitamin C.Under anesthesia and endotracheal intubation,Monitoring body surface electrocardiogram,cervical sympathetic nerve activity,Programmed Electrical stimulation(PES)was used to measure ventricular effective refractory period(VERP),monophasic action potential and ventricular arrhythmia.(2)Intraperitoneal injection of 4-methylcalechol(4-MC)to promote the surface of the heart sympathetic sprouting model: Rats were randomly divided into normal group(PBS)and experimental group(4-MC).The experimental group was given 4-MC for 30 days to promote sympathetic sprouting,and the normal group was given the same dose of PBS.Under anesthesia and endotracheal intubation,Monitoring body surface electrocardiogram,cervical sympathetic nerve activity,Programmed Electrical stimulation(PES)was used to measure ventricular effective refractory period(VERP),monophasic action potential and ventricular arrhythmia.Results:(1)The RR value of AMI+Vc group was significantly higher than that of the other three groups(p<0.05).The QRS wave in AMI+Vc group was significantly higher than that in sham+Vc group and AMI+6OHDA group(P<0.05).The QT interval in AMI+Vc group was significantly higher than that in sham+Vc group and AMI+6OHDA group(p<0.05).P wave,PR interval,ERP in each group had no statistical difference.APD50 and APD90 in non infarct area of AMI +Vc group were significantly longer than that in sham+Vc group and sham+6-OHDA group(P<0.05).APD50 and APD90 in peri infarct area of AMI +Vc group were significantly longer than that in other three groups(P<0.05).There was no significant difference in the frequency of APD alternans among the groups,but the frequency of myocardial infarction was lower than that of the non infarct group.The rats in group AMI+VC were more likely to be induced ventricular arrhythmia,but no arrhythmia was induced in 6-OHDA rats.After the increase of sympathetic discharge,the ventricular arrhythmia was induced in rats,and no ventricular arrhythmia was observed in 6-OHDA rats.There was no significant difference in carotid artery pressure,but the blood pressure of sham+VC group was higher than that of the other three groups.(2)4MC promotes sympathetic sprouting on the surface of the heart.However,there was no significant difference between the two groups in body surface electrocardiogram,ventricular effective refractory period,carotid blood pressure andventricular arrhythmia.APD90 in 4MC group was significantly longer than that in normal group(p<0.05).There was no significant difference between the two groups in the frequency of APD alternans,but the 4MC group was slightly lower than that of PBS group.Conclusion: 1.6-OHDA denervation can reduce the occurrence of ventricular arrhythmias after myocardial infarction in rats.2.4-MC promotes sympathetic sprouting in the normal rat,which can prolong the monophasic action potential duration of left ventricle,but can not increase the incidence of arrhythmia.3.The sympathetic nervous system may be involved in the occurrence of ventricular arrhythmia in pathological state,and blocking the release of sympathetic neurotransmitter may reduce the incidence of ventricular arrhythmia,even malignant ventricular arrhythmia. |
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