a Representative images showing the M-mode echocardiograms of rats treated for 1 month and 3 months. b Changes ininterventricular septum thickness at diastole (IVSd), left ventricular posterior wall end-diastolic thicknesses (LVPWd), and left ventricular mass index (LVMI) over time measured by echocardiography. c–f Measurement of left ventricular diastolic inner diameter (LVIDd), left ventricular systolic inner diameter (LVIDs), ejection fraction (EF), and fractional shortening (FS) (WKY group: n = 6; SHR group: n = 6; Captopril group: n = 5; harmine group: n = 7). All data are expressed as mean ± SEM. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001 by two-tailed Student’s t test compared with SHR group. #P < 0.05, ##P < 0.01, ###P < 0.001, ####P < 0.0001 by two-tailed Student’s t test compared with WKY group.