Figure 6. Impaired sustained exocytosis in Wrb‐deficient IHCs.

1. Ca²⁺ current–voltage relationship of P14–P17 IHCs of Wrb ^fl/fl:Cre ^A (n = 17 IHCs) and Wrb ^+/+:Cre ^A (n = 15 IHCs) mice in 2 mM extracellular [Ca²⁺] showed no change in amplitude or voltage dependence of Ca²⁺ currents. Data are represented as means ± SEM.
2. Representative Ca²⁺ current (top) and C_m changes (bottom) in Wrb ^fl/fl:Cre ^A and Wrb ^+/+:Cre ^A IHCs in response to 20‐ms step depolarizations to −14 mV (the potential eliciting the maximum Ca²⁺ current).
3. Representative Ca²⁺ current (top) and C_m changes (bottom, finite impulse response filtered) in Wrb ^fl/fl:Cre ^A and Wrb ^+/+:Cre ^A IHCs in response to 100‐ms step depolarizations to −14 mV.
4. Exocytic ΔC_m (top) and corresponding Ca²⁺ current integrals, Q_Ca (bottom) for various depolarization durations. Data are grand averages of the cells' means. Exocytic ΔC_m was reduced in the knockout from 20 ms onwards, indicating reduced sustained exocytosis. Data from Otof ^Pga/Pga animals were replotted for direct comparison from Pangrsic et al (2010). Data represent means ± SEM; *P < 0.05; **P < 0.01.
5. ΔC_m/Q_Ca2+ ratio indicates a lower efficacy of Ca²⁺ influx in driving exocytosis in Wrb ^fl/fl:Cre ^A IHCs, for stimuli of 20 ms or longer. Data represent means ± SEM; **P < 0.01; ***P < 0.001.