Fig. 2.

The effect of holding potential on currents produced in the presence of 500 µM external thiocyanate (SCN⁻). A–C: families of whole cell currents evoked in the same retinal pigment epithelial (RPE) cell from a holding potential of 0 mV (A), −60 mV (B), or −120 mV (C). The zero-current level is shown by the horizontal line to the left of each family of currents. The interval between the start of voltage steps was 7 s for holding potential (HP)  = −120 mV and 3 s for HP = −60 mV and HP = 0 mV. The pipette and bath solutions contained 140 mM Cl⁻ and 145.6 mM Cl⁻, respectively. D: summary of similar experiments (repeated measures in 7 cells from 2 C57BL/6J mice) showing current-voltage (I-V) plots of instantaneous current obtained from holding potentials of −120 mV (●), −60 mV (○), and 0 mV (▼). Symbols represent means and bidirectional error bars represent SE. Voltages are corrected for liquid junction potentials and the voltage drop across series resistance (R_s). Membrane potential (V_m) corrected for voltage errors averaged −110.0 ± 0.8 mV, −53.1 ± 0.2 mV, and +5.4 ± 0.1 mV at holding potentials of −120 mV, −60 mV, and 0 mV, respectively. The mean current amplitudes for the three holding potentials are significantly different from each other at all voltages, except for HP = −120 mV vs. HP = −60 mV at +10 mV (P < 0.05, two-way ANOVA followed by Tukey’s multiple-comparison test). E: dependence of reversal potential (E_rev, ●, left y-axis) and intracellular SCN⁻ concentration predicted for passive distribution (○, right y-axis) on holding potential. Symbols represent means and error bars represent SE (n = 7; P < 0.005, two-way ANOVA followed by Tukey’s multiple-comparison test).