Figure 8.

Membrane currents, resting potentials and τ_m in gerbil IHCs. Saturating MT currents in apical-coil gerbil IHCs exposed to 1.3 mM Ca²⁺ (A) and endolymphatic Ca²⁺ (0.02 mM) (B). Note the larger MT current amplitude and increased P_OPEN at rest compared to 1.3 mM Ca²⁺. In 0.02 mM Ca²⁺ about 20 per cent of the maximum MT current was activated at rest and this was abolished by 0.2 mM DHS. In (A) and (B) T= 24°C. (C–E) Voltage-dependent K⁺ currents in apical gerbil IHCs. Current records for voltage steps in 10 mV nominal increments (C), steady-state current-voltage (D) and conductance-voltage relationships (E) in a P18 IHC, T= 36 °C. Conductance G_K was determined as described for OHCs (Figure 5) and the conductance-voltage relation was fitted with a single Boltzmann where G_{K, MAX}, V_0.5, V_S are: 580 nS, −26 mV, 11 mV. (F) Voltage responses to current steps in apical IHCs with hair bundle exposed to 1.3 mM Ca²⁺, 0.02 mM Ca²⁺ and 0.2 mM DHS + 0.02 mM Ca²⁺. τ_m from fitting voltage onsets (dashed lines): 1.0 ms (1.3 Ca²⁺), 0.8 ms (0.02 Ca²⁺), 1.0 ms (0.02 Ca²⁺ + DHS). (G) IHC resting potential (mean ± SEM; n = 4) for the three conditions in (F). (H) Time constant τ_m (mean ± SEM) from recordings as in (F).