乙酰胆碱对豚鼠外毛细胞的电压依赖性外向整流钾电流的影响

Effects of ACh on Voltage-dependent Outwardly Rectifying Potassium Currents in Isolated Outer Hair Cells in Cochlea of Guinea Pig

目的 观察乙酰胆碱（ＡＣｈ）对不同长度豚鼠耳蜗外毛细胞（ＯＨＣ）电压依赖性外向整流钾电流的影响，分析 ＡＣｈ对钾电流激活动力学的影响。方法 全细胞膜片钳技术。结果１００μｍｏｌ／Ｌ的ＡＣｈ对短ＯＨＣ电压依赖性外向整流钾电流的影响较大，刺激电压为５０ｍＶ时，最大外向电流的幅度增加了３４．８％。ＡＣｈ对峰电流的影响大于稳态电流，改变了外向整流钾电流的动力学特征。ＡＣｈ将ＯＨＣ的零电流电位向超极化方向移位约５ｍＶ。1００μｍｏｌ／Ｌ的ＡＣｈ使ＯＨＣ电压依赖性外向整流钾电流的激活动力学发生改变，Ｖ（１／２）＝（－５２．３８±３．９８）ｍＶ，较作用前明显超极化，激活的电压敏感性也提高，Ｓ＝（４０±４．１４）ｍＶ（ｎ＝５）。结论ＡＣｈ增加了ＯＨＣ电压依赖性外向整流钾通道的电导，使通道的激活电压向超极化方向移位。ＡＣｈ的作用是使ＯＨＣ超极化。

Objective To observe the effect of ACh on outwardly rectifying potassium currents in isolated outer hair cells(OHCs) with variant length and to analyze effects of ACII on kinetics of the currents. Methods The whole cell patch-clamp technique was used. Results 100 μmol/L ACh induced greater effects on outwardly rectifying potassium currents in short OHCs. The maximal amplitude of the outward currents increased by 34.8% in the presence of 100 μmol/L ACII when conditioning potential was 50 mV. ACh effects on the peak currents were greater when compared to the effects on the steady-state currents and changed the shapes of the currents. ACII caused a hyperpolarizing shift of zero current potential of 5 mV. Kinetics of the currents were changed by 100 μmol/L ACh which induced significantly more hyperpolarizing than control, with increased potential sensitivity of activation, V1/2(Ach) =(-52.38 ± 3.98) mV, SACh =(40 ± 4.14) mV(n= 5). Conclusion ACh increased the conductance of outwardly rectifying K + channel in a voltage dependent manner and caused a hyperpolarizing shift of activation potential. Effect of ACh was to hyperpolarize the membrane potential of OHCs from rest.