Figure 4. K_v3.1b relaxes from a pre-active state in the presence of 4-AP.

(a) Ig_deac currents of K_v3.1b in the presence of 1 mM 4-aminopyridine (4-AP) with different activating pulse durations at +40 mV. (b) Top panel, superposition of Ig_deac at −60 mV on a 1-ms (black), 5-ms (blue) and 10-ms (red) long depolarization to +40 mV. Bottom panel, superposition of the same Ig_deac currents after normalization. Note the gradual deceleration in Ig_deac decay as the activating pulses are prolonged. (c) Ig_deac kinetics (τ_Igdeac) as a function of depolarization time in the presence of 1 mM 4-AP, displayed as mean±s.e.m. (n=5). Even in the presence of 1 mM 4-AP there was a noticeable deceleration in τ_Igdeac that developed relatively quickly. For example, compare τ_Iideac on a 0.3-ms (pink) and a 3-ms (green) activating pulse at+40 mV. (d) Weighted τ_Igdeac at −60 mV as a function of the activating pulse duration in both the absence (grey) and presence of 1 mM 4-AP (red), shown as mean±s.e.m. (n=5). τ_Igdeac was slowed down in presence of 4-AP, a deceleration that developed over a similar time window as the fast slowing process (τf) in control conditions.