Effects of 1 mM Ni²⁺ on currents carried by 2 mM Ca²⁺ (A) or 2 mM Ba²⁺ (B), using the IIV protocol. Cells were depolarized from a holding potential of −100 to +200 mV for 2 ms, to activate the channels and relieve most inhibition by Ni²⁺, followed by voltage steps in 10-mV increments from +100 to −150 mV for 100 ms. Only the initial portion of the tail currents is shown, for voltage steps in 50-mV increments. Records are shown before application of Ni²⁺ (left column), in 1 mM Ni²⁺ (middle column), and after washout of Ni²⁺ (right column). Dashed lines indicate zero current following leak subtraction. 3-kHz digital Gaussian filter. Cells b050825 (A), d051019 (B).