Kinetics of vesicle release increases with HC maturation.

<p>Cochlear apical HCs were voltage-stepped from holding potential of −90 mV to -10 mV for increasing duration (20 to 3000 ms). To avoid synaptic depression, each pulse of varying duration was separated by a 30 s recovery period. A) Comparative mean ΔC_m responses (RRP+SRP) recorded in P2 (n = 8) and E10 (n = 6) apical HCs. B) RRP depletion, corresponding to the first 100 ms of release, was fitted with a single exponential with τ = 89, 75, 48, and 39 ms at E10 (n = 6), E12 (n = 7), E16 (n = 9) and P2 (n = 8), respectively. (C–D) Comparative ΔC_m responses (RRP + SRP) recorded in P2 or E12 apical HCs using 0.5 (as in A and B) or 2 mM intracellular EGTA (n = 4 and 5, respectively). Contrary to the SRP, note that the RRP (D) is not affected by 2 mM EGTA in both mature and immature HCs.