Effects of retigabine on KCNQ currents are concentration dependent. A, Experiments were performed in high extracellular K+ (25 mm) solution to enhance the tail currents. A family of currents for KCNQ2/3 and the voltage protocol under these conditions are shown. Application of retigabine led to a slowing in the rate of decline of the KCNQ tail current (inset). B, Representative activation curves for KCNQ2/3 and KCNQ4 generated in the absence (■) and presence of 1 μm (▪), 3 μm (▴), 10 μm (●), 30 μm (▾), 100 μm(♦), and 300 μm (✳) retigabine. For KCNQ4, 1 mm retigabine (⋄) was also applied.