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目的：研究丙咪嗪对大鼠心室细胞瞬间外向钾电流（Ｉｔｏ）的抑制作用．方法：膜片箝全细胞记录法．结果：丙咪嗪对Ｉｔｏ有浓度依赖性抑制作用，ＩＣ５０为６０μｍｏｌ·Ｌ－１，并明显加速该电流的灭活时程．在不同的测试电位下，丙咪嗪对该电流的抑制百分率没有差别．丙咪嗪对Ｉｔｏ的稳态激活和灭活曲线的半数膜电位都无明显影响，对Ｉｔｏ灭活后的再复活时程有延长趋势，但不显著（τｃｏｎｔｒｏｌ＝３７±１１ｍｓ，τｄｒｕｇ＝５８±１７ｍｓ，Ｐ＞００５），但可明显加速条件刺激时程对Ｉｔｏ的灭活（τｃｏｎｔｒｏｌ＝２２±８ｍｓ，τｄｒｕｇ＝１４±５ｍｓ，Ｐ＜００５）．结论：丙咪嗪对大鼠心室细胞瞬间外向钾电流有浓度依赖性和电压非依赖性抑制作用，作用特点属于开放通道阻断．
Objective: To study the inhibitory effect of imipramine on ventricular transient outward potassium current (Ito) in rats. Methods: patch clamp whole cell recording method. RESULTS: Imipramine inhibited Ito in a concentration-dependent manner with an IC50 of 6.0 μmol·L-1 and significantly accelerated the inactivation of Ito. There was no difference in the percent inhibition of this current between the different test potentials. Imipramine had no significant effect on Ito steady-state activation and half-membrane potential of the inactivation curve, but had no significant effect on the resuscitation duration after Ito inactivation (τcontrol = 37 ± 11ms, τdrug = 58 ± 17ms, P> 005), but could significantly accelerate the inactivation of Ito (τcontrol = 22 ± 8ms, τdrug = 14 ± 5ms, P <005). CONCLUSION: Imipramine has a concentration-dependent and voltage-independent inhibitory effect on transient outward potassium current in rat ventricular cells, which is characterized by an open channel blockade.