Motor Noise in Outer Hair Cells

摘要

Outer hair cells in the mammalian ear has a membrane based motor which directly converts electrical energy into mechanical energy. Such a motor is associated with the function of these cells in providing feedback to vibration in the inner ear. To obtain insights into the motor mechanism, we examined kinetics of charge transfer across the membrane in two different modes. One is to monitor charge transfer induced by changes in the membrane potential as an excess membrane capacitance. The other is to measure spontaneous flip-flops of charges across the membrane under voltage clamp condition as current noise. The noise spectrum of current was inverse Lorentzian and the capacitance was Lorentzian as theoretically expected. The characteristic frequency of the capacitance was about 10 kHz and that for current noise was about 30 kHz. This result is inconsistent with the prediction. The difference can be explained by a reciprocal effect of being a piezoelectric motor in that mechanical motion which is subjected to friction affects the frequency response.