Fig. 3: Kcnq2/3 current responses to square voltage steps are different from those of Kcnh7 channels.
From: Kcnq (Kv7) channels exhibit frequency-dependent responses via partial inductor-like gating dynamics
a Resistor-inductor-capacitor (RLC) circuit with a leaky inductor (RL [30 MΩ] and L [10 MH]) and resistance of the recording electrode (Re [5 MΩ]). R = 100 MΩ, C = 200 pF. b Square input voltage steps with amplitudes of 5 and 10 mV. c Simulated currents flowing through the leaky inductor (IL in a) in response to square input voltage steps. Currents were simulated using LTspice XVII. d, e Voltage protocols applied to Kcnq2/3-expressing cells (upper traces) and representative Kcnq2/3 currents (lower traces) in response to ±5 (d) and ±10 (e) mV voltage steps. Kcnq2/3 currents were calculated by subtracting the currents recorded in the presence of XE991 (20 μM) from those recorded in its absence. f, g Expanded traces in response to ±5 (f) and ±10 (g) mV voltage steps in the periods marked by dotted rectangles in d or e. h, i Representative Kcnq2/3 conductance calculated from the data in d and e. The conductance was calculated by dividing the current amplitude by the driving voltage (holding potential—theoretically calculated K+ equilibrium potential [−98 mV]). j Steady-state Kcnq2/3 conductance (green bars in h and j) relative to that at −40 mV (n = 9). Green dots represent individual data and larger red dots with bars represent the mean ± SEM. **P < 0.01, *P < 0.05 (repeated measures one-way ANOVA; post-hoc Holm–Šidák test). k, l Average conductance relative to the baseline before onset of 5 and 10 mV depolarizing pulses. Black arrowheads show the points at which transient opposing conductance changes were expected to be observed. Shaded areas indicate the mean ± SEM. m, n Magnitudes of opposing conductance changes (arrowheads in k and l) relative to the steady-state conductance (black bars in k and l) before onsets or offsets of 5 (m) or 10 (n) mV depolarizing voltage steps (n = 9). Green dots represent individual data, and red bars represent the mean ± SEM. o, p Average relative current of Kcnh7  channels in response to depolarizing voltage steps. Shaded areas indicate the mean ± SEM. q, r Similar to k and l, but showing the average relative conductance of Kcnh7 currents. Shaded areas indicate the mean ± SEM. s, t Magnitudes of opposing conductance changes (arrowheads in q and r) relative to the preceding steady-state conductance (black bars in q and r) (n = 7). Green dots represent individual data, and red bars represent the mean ± SEM.
