The effects of varying intracellular cations on rate of charge return. (A) Representative current traces recorded using an intracellular TEA⁺ solution were evoked by 12-ms depolarizing pulses applied in 10-mV increments from a holding potential of −100 mV. (B) Gating currents recorded with Cs⁺_i. (C) Representative currents obtained by depolarizing the membrane to 0 mV for 50 ms before repolarization to a series of pulses from −40 to −190 mV with TEA⁺_i. Linear membrane leak was subtracted online using a −P/8 leak subtraction protocol from a subtraction holding potential of −140 mV. (D) Return of charge in the presence of intracellular TEA⁺ and Cs⁺ was measured during an 11-ms charge integration period after the depolarizing pulse and plotted against voltage. The Q_off-V for Cs⁺_I had V_0.5 = −38 ± 1.8 mV, z = 2.8 ± 0.2 (n = 3). Using intracellular TEA⁺_i did not significantly affect Ig_ON (Q_on-V: V_0.5 = −30.3 ± 1.4 mV, z = 2.3 ± 0.3; n = 5). The Q_off-V for TEA_i (Δ) gave fitted values of V_0.5 = −125.9 ± 3.9 mV and z = 2 ± 0.2 (n = 3). Error bars represent SEM.