Figure 3.

Ca²⁺ dependence of exocytosis in adult gerbil IHCs. A, I_Ca and ΔC_m from apical (low-frequency, gray) and basal (high-frequency, black) IHCs. Voltage protocol is as in Figure 1. For clarity, only responses at −81 and −11 mV are shown. B, Average peak I–V and ΔC_m–V curves in apical (P22–P34; n = 15) and basal (P20–P30; n = 13) IHCs. C, Synaptic transfer functions obtained by plotting average ΔC_m against the corresponding I_Ca between −71 mV and near −11 mV from B for apical and basal IHCs. The fits are according to Equation 1. D, Single data points used to generate averages in C from apical and basal IHCs. Fits are as in C. E, Synaptic transfer functions from apical and basal IHCs showing average responses at the membrane potential at which the peak I_Ca from the I–V curve occurred (from approximately −11 to −1 mV) in different Ca²⁺ concentrations. Fits are using Equation 1. F, Single data points used to generate averages in E from apical and basal IHCs plotted on a double logarithmic scale. Fits are as in E. In both E and F, the number of observations at each Ca²⁺ concentration (0, 0.6, 1.3, 2.5, 5, 10 mm) were as follows: apical 7, 6, 26, 11, 13, 5 (from 26 IHCs); basal 7, 4, 15, 4, 11, 8 (from 16 IHCs). Error bars indicate SEM.