Figure 5.

Membrane capacitance versus frequency measured by high-resolution frequency-dependent NLC of OHCs, the meno presto model, the fast two-state model, and the electrical model. (A) Averaged OHC NLC (n = 5) measured using the chirp protocol between 300 and 5000 Hz with 140 mM intracellular chloride. Note the rapid decline of peak capacitance. (B) Another group average of OHCs with 1 mM intracellular chloride (n = 6). The peak NLC decline is also evident in this condition. (C and D) C_m versus frequency as measured by the meno presto model at 140 mM and 1 mM chloride, respectively. The stimulus protocol and analysis were the same as the biophysical measures. Note the similarity to the biophysical data. (E) C_m versus frequency as measured by the fast two-state Boltzmann model (forward/backward rate constants of 1.5e5 s⁻¹). Note the absence of NLC decline across frequency. (F) C_m versus frequency as measured by the slower two-state Boltzmann model (forward/backward rate constants of 0.5e4 s⁻¹). Note the gradual roll-off due to reduced single-exponential transitions. (G) C_m versus frequency as measured by the electrical cell model with R_s = 10 MΩ, R_m = 300 MΩ, C_m = 17 pF, all nominal. Note the flat C_m response across frequency and voltage. (H) C_m versus frequency as measured by the same electrical model, with an additional 5 pF C_m switched in using a magnetically activated reed relay with minimal additional stray capacitance. To see this figure in color, go online.