Figure 3.

Changing external [K⁺] when channels were activated had little effect on macroscopic conductance. To measure macroscopic conductance, 10 mV, 5-ms depolarizations were superimposed on the depolarization to 0 mV. (Trace 1) Channels were activated in the absence of external K⁺. At the arrow, external [K⁺] was changed to 10 mM. In this cell, conductance increased by 21% with essentially no change in current magnitude. In eight cells, the average conductance change was 22.7 ± 2.6%. (Trace 2) Channels were closed and reactivated in the presence of 10 mM external K⁺. In this cell, conductance increased by 110%. In eight cells, conductance increased by 93.1 ± 7.2%.