Figure 7. Qd-promoted irreversible drop of G_K.

A, control I_K evoked by a +40 mV/30 ms pulse in Na_o/K_i (left panel). After the stability of I_K was tested (see B) the cell was superfused with Na_o+ 0.1Qd for 45 s and 22 +40 mV pulses were applied at 0.25 Hz (middle panel). Then, the cell was superfused for 1.25 min with the Na_o solution and channels were activated as in the control (right panel). B, I_K as a function of the time of recording of the experiment in A, as indicated. The points at t < 0 (labelled Before) are control I_K, prior to the addition of Qd. The points at t≥ 0 (labelled After) are I_K recorded after the washing episode with Na_o (i.e. after Qd removal, as in the right panel in A). At the time indicated by the arrow labelled 40K_o the cell was superfused for 1.25 min with 40K_o solution (and afterward the cell was left in this solution for the remainder of the experiment, as indicated). The dotted line serves to best show the lack of recovery of I_K. C, I_K recovered immediately after washing the cell with Na_o (After in B) superimposed on I_K at the end of the recording (in 40K_o). Addition of 40 mm did not allow the recovery of I_K.