Objective To investigate the long-term effects of imidapril (IMI) on action potential and calcium and potassium currents in rabbit left ventricular hypertrophic myocytes.Methods Rabbits were randomly divided into three groups: IMI-treated, hypertrophic and sham-operated control groups. Cardiac hypertrophy was induced in hypertrophy group by partial ligation of the abdominal aorta. In the IMI-treated group, the rabbits were administered IMI (1.5 mg·kg-1·d-1) for 8 weeks after surgery. In the sham-operated control group, the animals underwent an abdominal laparotomy without further procedure. Whole-cell patch clamp technique was used to record ionic currents.Results Membrane capacitance was larger in hypertrophic cells than in sham-operated cells or IMI-treated cells. Action potential duration was lengthened in hypertrophic cells and was remarkably shortened by IMI. The density of ICa,L was reduced from 12.8±0.7 pA/pF in the sham-operated cells, to 7.7±0.8 pA/pF in hypertrophic cells, while it resembled the control cells after IMI treatment (11.9±1.0 pA/pF). After IMI treatment, the density of IKs,tail was enhanced from 2.5±0.1 pA/pF in hypertrophic cells to 4.7±0.6 pA/pF (n=7, P<0.01), which was similar to the sham-operated cells. The densities of Ito and IK1 were significantly increased in IMI-treated cells, from 3.8±0.4 pA/pF and 3.7±0.5 pA/pF in the hypertrophic cells to 6.4±0.8 pA/pF and 6.5±0.3 pA/pF, respectively, but the IKr densities were not different in the three groups.Conclusion IMI could reverse the increase in membrane capacitance in hypertrophic cells, shorten action potential duration, and increase the densities of ICa, L, IKs, Ito and IK1 in hypertrophic cells.