Figure 4. The p.Arg497* mutation does not affect the maturation of voltage-gated ion conductances in OHCs.

(A) Whole-cell patch-clamp recordings of the outward and inward ionic conductances in OHCs of cochlear explants of Tric^+/+ mice. The membrane currents (top traces) were evoked by depolarizing and hyperpolarizing voltage steps (bottom traces) of various step potentials from –120 mV to +20 mV. OHCs were maintained at a holding potential of –60 mV between acquisitions. (B) Whole-cell currents in OHCs of the Tric^R497X/R497X mice were comparable to those observed in OHCs of wild-type littermates. (C) The steady-state currents measured at 145 ms after onset of the voltage step were identical in OHCs of Tric^R497X/R497X (white circles) and Tric^+/+ (black circles) mice. (D) Statistically nonsignificant differences in the speed of activation of voltage-gated conductances. The current response measured at 3 ms after beginning of the voltage step is shown. The differences in responses (mean ± SEM) of Tric^R497X/R497X (white circles, n = 21) and Tric^+/+ (black circles, n = 15) OHCs were largely nonsignificant except at 1 point at –120 mV (P < 0.05). The inset shows the time constant (τ) of current activation. The same recordings contributed to C and D. The age of the cultured organ of Corti was P3 plus 3–5 days in vitro.