Figure 2.

Hair cell Ca²⁺ currents and capacitance changes (ΔC_m). Voltage-clamped hair cells were depolarized from a holding potential of −90 to −30 mV for various durations with 2 mm EGTA (A) or with 10 mm BAPTA (B) as internal Ca²⁺ buffers. Top panels, Evoked Ca²⁺ currents with 20 ms (red), 500 ms (blue), 1 s (green), and 3 s (black) pulses. Bottom panels, The membrane capacitance (C_m) increases with the duration of the step depolarizing pulse [20 ms (red), 100 ms (purple), 500 ms (blue), 1 s (green), and 3 s (black)]. Note the fivefold difference in vertical scales indicating the greatly reduced exocytosis when 10 mm BAPTA is present in the hair cells. Note also the nearly twofold larger ΔC_m jump for 3 s versus 1 s depolarizing pulses with EGTA, whereas this difference is much smaller with BAPTA. This suggests that 10 mm BAPTA inhibits vesicle recruitment. When 2 mm EGTA is present in the hair cell, we also observed greater Ca²⁺ current inactivation with long depolarizing pulses.