Figure 1.

Properties of calcium currents in immature OHCs from Otof^+/+ and Otof^−/− mice. A, Examples of I_Ca recorded in OHCs of Otof^+/+ (●) and Otof^−/− (○) P2 mice. Currents were evoked by 10 ms voltage steps from a −82 mV holding potential to 0 mV. Single-exponential fits (solid lines) show similar activation kinetics, with τ = 342 μs (●) and 340 μs (○). B, Comparative I_Ca–V curves in OHCs of Otof^+/+ and Otof^+/− (●; n = 11) and Otof^−/− (○; n = 9) mice. C, Average normalized I_Ca conductance in Otof^+/+, Otof^+/−, and Otof^−/− mice. Continuous lines are Boltzmann fits with the following parameters: G_max = 2.6 ± 0.4 and 3 ± 0.2 nS; V_1/2 = −12.2 ± 0.5 and −12.3 ± 0.5 mV; and k = 10.1 ± 0.4 and 9.9 ± 0.5 mV for Otof^+/+ and Otof^+/− and Otof^−/− OHCs, respectively. D, Peak calcium current density (expressed in pA/pF) as a function of postnatal age in Otof^+/+ and Otof^+/− OHCs. The numbers of tested cells are indicated on the histogram. Note the drastic decrease of I_Ca density after P6. E, Example of a train of spontaneous action potentials recorded from a P3 Otof^+/− OHC. The voltage recording was made in the absence of any current injection, in artificial perilymph with 10 mm calcium, at RT. F, Enlarged view of two action potentials.