Abstract: Objective To study the changes of myocardial hypertrophy and myocardial fibrosis in spontaneously hypertensive rats (SHR) with cardiac sympathectomy induced by 6-hydroxydopamine (6-OHDA) or cervical sympathectomy. Methods Thirty 7-week-old male SHRs were randomly divided into three groups:sham operation group (n=10),operation group (n=10) and 6-OHDA group (n=10) and they were reared for 7 weeks.The cardiac structure and function were measured by echocardiography,and left ventricular mass index was calculated.Biomedical signal acquisition and processing system was used to detect hemodynamic parameters.CollagenⅠ,CollagenⅢ and connective tissue growth factor (CTGF) were detected by real-time quantitative PCR. Results Compared with sham operation group,tyrosine hydroxylase (TH) expression decreased significantly in 6-OHDA group and operation group (2.17±0.28)% and (1.06±0.24)% vs (5.34±0.32)%;P<0.05,respectively,and no significant difference was found between 6-OHDA group and operation group (P=0.547).Systolic blood pressures and heart rates in sham operation group,operation group and 6-OHDA were in a decreasing manner (all P<0.001),with significant differences between any of the two groups.Compared with sham operation group,left ventricular mass index (LVMI),thickness of ventricular septum,left ventricular posterior wall,left ventricular end-diastolic and end-systolic diameters were significantly lower in operation group and 6-OHDA group (P<0.05);also,the expressions of myocardial fibrosis markers CollagenⅠ,CollagenⅢ and CTGF genes were significantly lower (P<0.05);however,there was no significant difference in these indicators between the latter two groups. Conclusion Myocardial hypertrophy and myocardial fibrosis in SHR with cardiac sympathectomy are alleviated significantly by injecting 6-OHDA or cervical sympathectomy.The chemical sympathetic denervation model established by 6-OHDA can be used as an alternative method for those who are intolerant to sympathectomy.