Figure 5.

SHC properties linked to voltage-evoked bundle motion. (A) Non-linear capacitance in a SHC determined (see Methods) as the difference, ΔC_m, between membrane capacitance without and with perfusion of 10 mM Na⁺ salicylate. Pre- and post-controls were obtained by using the control prior to salicylate application (filled circles) and the wash after salicylate (open circles) for the subtraction and indicate full recovery from the salicylate. The ordinate is scaled by the linear capacitance, 6.4 pF. Each set of points was fit with equation 1, with V_0.5 = 7 mV, z = 0.71 (filled circles) and V_0.5 = 25 mV, z = 0.63 (open circles) and ΔC_m = 22 fF/pF for both. (B) Non-linear capacitance in two SHCs recorded with normal intracellular saline containing 161 mM Cl⁻ (filled circles) and low Cl⁻ in which all but 20 mM CsCl was replaced by Cs⁺ aspartate (open circles). Points fit with equation 1, with V_0.5 = 4 mV, z = 0.57, linear capacitance = 5.7 pF (normal) and V_0.5 = 60 mV, z = 0.62, linear capacitance = 5.5 pF (low Cl⁻). Note positive voltage shift with low Cl⁻ intracellular. (C). Voltage-induced hair bundle motion in patch clamped cell, SHC1, and in adjacent cell, SHC2 (not clamped), with return control from original cell SHC1. Bundle motion of nearby SHC suggests force generation in cell body or cuticular plate. Polarity and magnitude of bundle motion obtained by sequential calibration of bundle-1 and bundle-2 images. (D). Schematic of experiments in (C), polarity, Ab (abneural) and N (neural) sides of papilla.