Figure 4.

Effects of K⁺ channel blockers on whole-cell and single-channel currents. (A) Whole-cell currents after cell swelling by 28% HYPO solution, with NaCl bath and KCl pipette solution (control) and in the presence of 5 mM Ba²⁺ in the bath (+Ba²⁺). (B) Percentage of blocking of K⁺ currents by 5 mM Ba²⁺ (n = 5), 1 mM Gd³⁺ (n = 4), or 5 mM TEA⁺ (n = 4). The control current at E_Cl was 700 ± 120 pA. The effects of these concentrations of Ba²⁺ and Gd³⁺ were statistically significant, whereas there was no effect of TEA⁺. (C) Single-channel records on outside-out patches at 20 mV, control, and 5 mM Ba²⁺. Single-channel openings are clearly observed in the expanded traces. (D) Percentage of blocking by 5 mM Ba²⁺, 1 mM Gd³⁺, or 5 mM TEA⁺ (n = 3 experiments). The lowest current level in 5 mM Ba²⁺ was assumed to be 0. Blocks by 5 mM Ba²⁺ and 1 mM Gd³⁺ were statistically significant.