Figure 2.

The transient block of the Ca²⁺ current requires a certain period of time at the more depolarized holding potential of −60 mV. A, Ca²⁺ currents were recorded from hair cells held at −90 mV using a 20-ms-long pulse to −30 mV followed by pre-depolarization to −60 mV for 10–1000 ms. Different colors represent different durations of the pre-depolarization from −90 to −60 mV. Ca²⁺ currents started showing a transient block with 75 ms of pre-depolarization (arrow). B, A depolarization from −90 to −60 mV evokes a small, non-inactivating Ca²⁺ current in the hair cell. C, Ca²⁺ currents elicited by the 20 ms pulses with various pre-depolarization (10, 75, 200, and 1000 ms) were superimposed. The transient block becomes clearly larger as the duration of the pre-depolarization increases.