Figure 2.

K_slow current is K⁺ selective. (A, bottom) After the train of depolarizations, the membrane potential was held for 10 s at voltages between −40 and −80 mV as indicated schematically by the pulse protocol. (A, top) Membrane currents recorded at −50 mV after the train when the extracellular medium contained 3.6 or 15 mM K⁺ as indicated. Note that the currents go in opposite directions. (B) The peak tail currents recorded at membrane potentials between −80 and −40 mV before and after elevation of extracellular K⁺ from 3.6 mM (▪) to 15 mM (▴). The amplitude of the current was measured as illustrated in B. The arrows indicate the reversal potentials recorded at low and high extracellular K⁺.