Effects of ACh on Voltage-dependent Outwardly Rectifying Potassium Currents in Isolated Outer Hair Cells in Cochlea of Guinea Pig / 听力学及言语疾病杂志

ABSTRACT

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 ?mol/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 ?mol/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 ?mol/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.