Figure 1.

Kv1.2 gating currents display slow OFF gating currents after depolarization to potentials that populate the open state. (A) Representative gating currents recorded from tsA201 cells transfected with Kv1.2 using intracellular NMG⁺ and extracellular TEA⁺ solutions with the displayed voltage protocol. The leak currents were subtracted using a −P/8 leak subtraction protocol from a subtraction holding potential of −100 mV (n = 9). (B) Individual representative gating current traces isolated from the same recording to illustrate the onset of slowing of the Ig_OFF current recorded at −100 mV after depolarizing steps from −50 to 10 mV in 20-mV increments. (C) Q-V relationships obtained from integrating Ig_ON (□, Q_on-V) and Ig_OFF (○, Q_off-V) for 11 ms. The normalized Q_on-V was fit with a Boltzmann equation that gave fitted values of V_0.5 = −28.6 ± 1.3 mV and z = 3 ± 0.2 (n = 9) for the Q_on-V. Also shown is the G-V relationship (Δ) constructed from isochronal tail current measurements at −40 mV for Kv1.2 currents recorded in standard ionic conditions, which gave fitted values of V_0.5 = −4.4 ± 2.8 mV and z = 1.9 ± 0.1 (n = 4) with a representative family of current traces from the displayed protocol inset. (D) The peak Ig_OFF currents from each cell were normalized and plotted against the voltage of the preceding depolarizing pulse. Error bars represent SEM.