Figure 4.

Reentry of Y³⁺ into open channels. (A) Effect of 1 μM Y³⁺ on tail currents. A 1-ms step to +200 mV was used to both activate channels and relieve Y³⁺ block. Currents are shown following repolarization to +80 mV, −40 mV, and −160 mV. Currents at +200 mV are off scale. 1.5 kHz Gaussian filter. (B) Acceleration of tail currents by Y³⁺. Tail currents were fitted by single exponentials in control conditions, and in four concentrations of Y³⁺. Values are not shown at +20 mV, near the reversal potential. n = 4–6. (C) Voltage- and concentration-dependent reblocking. For each cell, at each voltage, the blocking rate was calculated from tail current time constants in Y³⁺ and in control conditions (Eq. 1).