Fig. 4.

Functional estimation of the concentration and kinetics of endogenous Ca²⁺-binding sites in IHCs. (A) ΔC_m and Q_Ca in response to depolarization for 20 ms (probing the RRP) in WT and TKO IHCs using perforated-patch (black and light gray) and in KO IHCs using ruptured-patch configuration with different concentrations of the exogenously added synthetic Ca²⁺ chelators BAPTA and EGTA (shades of gray). (B) Difference in the ΔC_m and Q_Ca in response to 100 and 20 ms (probing the sustained exocytosis). When testing the sustained component of exocytosis 0.5 mM of either buffer was insufficient in Ca²⁺ buffering. On the contrary, 1 mM BAPTA (but not EGTA) significantly reduced the amount of RRP exocytosis (A). Asterisks denote significant difference vs. WT controls (P < 0.01, Student t test or Wilcoxon rank-sum test). From left to right, n = 18, n = 6, n = 5, n = 12, n = 10, n = 7, and n = 12 IHCs were analyzed.