Figure 4.

Sensor charge movements estimated from two-sine admittance analysis, off-current integration, or eM show low-pass frequency characteristics. (A) The AC measured specific sensor charge (Q_sp) corresponds to the integrated off-charge and shows that discrete measures of charge movement by AC admittance provide underestimates of the total prestin charge. (B) Q_sp (circles) and eM (triangles), which is known to be driven by voltage, display magnitudes that correspond to the predictions of the meno presto model (gray lines). Interrogation time is the geometric average of periods of the dual-sine protocol, the integration time of sensor charge, or the eM fundamental frequency period (see Results). The biophysical data and model indicate that regardless of chloride concentration (but at above-zero concentrations), positive voltage will move prestin into the compact state, asymptoting at the maximum sensor charge dictated by prestin membrane content. Data are derived from averages of multi-dual-sine currents (circles) and eM (triangles) from n = 5–8 OHCs. To see this figure in color, go online.