GxTX-594 modulates Kv2.1 conductance. (A) Representative Kv2.1-CHO current response under whole-cell voltage clamp. Cells were given 100-ms, 5-mV increment voltage steps ranging from −80 mV (blue) to +120 mV (red) and then stepped to 0 mV to record tail currents. The holding potential was −100 mV. (B) Kv2.1 currents from the same cell 5 min after the addition of 100 nM GxTX-594. Scale bars are the same for A and B. (C) Normalized conductance–voltage relationships from Kv2.1 tail currents before application of GxTX-594 (n = 13). Different symbols correspond to individual cells, and the green corresponds to cell in A. (D) Normalized conductance—voltage relationships in 100 nM GxTX-594 (n = 11). (E) Mean midpoint of each of four independent voltage sensors in the fourth-power Boltzmann fit (V_1/2) before (−31 ± 6 mV SD) and after (+27 ± 10 mV SD) 100 nM GxTX-594. ***, P < 0.0001 by Mann–Whitney U test. (F) Mean e₀ associated with Boltzmann fit (z) before (1.5 ± 0.3 e₀ SD) and after (1.0 ± 0.4 e₀ SD) 100 nM GxTX-594. ***, P = 0.0007 by Mann–Whitney U test. (G) Mean midpoint of conductance change in the fourth-power Boltzmann fit (V_mid) before (−2 ± 6 mV SD) and after (+73 ± 13 mV SD) 100 nM GxTX-594. ***, P < 0.0001 by Mann–Whitney U test.