The Inhibitory Effect Of Metoprolol On Sympathetic Nerve Remodeling After Acute Myocardial Infarction In Rats

Objective: To investigate the inhibitory effect of metoprolol on sympathetic nerver remodeling after acute myocardial infarction in rats.Materials and methods: 48 wistar rats suffered LAD occlusion operation successfully were randomly divided to myocardial infarction group(MI group) and metoprolol therapy group(MI+Blocker group),then these two groups were investigated at three different time-points,ie,3–day,7-day and 30-day . The rats in MI+Blocker group were administered by metoprolol at the dose of 10 mg·kg-1·d-1.And we assigned randomly the same amount of rats into every time-point ,which just suffered sham operation as control group.Use Power Lab to detect the ECG of mices,then calculate QT dispersion(QTd) in every group.Record the ECG of mice consecutively and score the arrhythmia in every group.At last, use immuohistochemical method to detect the density of sympathetic nerve in the peri-infarction zone .Results:The density of sympathetic nerve increased significantly in MI group at 7 day and 30 day time-points comparing with control group.And after the intervention of metoprolol ,the density of nerve fiber in peri-infarciotn zone decreased evidently at 30 day time-point(P<0.05)comparing the same time-point in MI group.After administration of metoprolol,there were significant decrease in both QTd and the arrhythmia score between MI group and MI+blocker group at every time-point (P<0.05),and the most magnitude of decrease in QTd and arrhythmia score occurred at 30 day time-point. Conclusion: Metoprolol can inhibit the remodeling of sympathetic never fiber after acute myocardial infarction and decrease QTd and arrhythmia,the effect on later at 30 day time-point is mediated partly by inhibiting nerve remodeling.