Figure 9. Calcium dependence of neurotransmitter release in adult IHCs from control and Syt IV knockout mice.

A and B, Ca²⁺ current (I_Ca) and changes in membrane capacitance (ΔC_m) from adult IHCs in response to voltage steps, in 10 mV increments, from the holding potential of −81 mV. Extracellular Ca²⁺ concentration, 1.3 mm. In A, only peak responses and those at −81 mV are shown. C, left panels show average ΔC_m traces from control and knockout IHCs; right panel shows the synaptic transfer curves obtained by plotting ΔC_m against I_Ca for voltage steps between −71 and −11 mV (B). Fits are according to eqn (1) (see Fig. 8). D, synaptic transfer curves, similar to those shown in C, but obtained by plotting the maximal I_Ca and ΔC_m values during the application of different extracellular Ca²⁺ concentrations. Figure modified from Johnson et al. (2010).