Representative whole-cell patch clamp currents with only Na+ or K+ as the major permeant ions. The compositions of the bath perfusates are indicated by the horizontal bars and the colors of the bars are identical to the colors in the corresponding graphs. A) Continuous trace recordings in symmetrical Na+-rich solutions (B2, P2; left panel) and K+-rich solutions (B3, P3; right panel). Voltage step protocols were applied every 16.7 seconds with holding at 0 mV and steps from +100 mV to -100 mV in 20 mV decrements. Individual step responses are shown in the lower panels and their locations within the continuous trace are indicated by the numbers in parentheses. Horizontal arrows indicate the zero current level. B) Current-voltage (I-V) relationships of the whole cell currents in the presence and absence of Benzamil (1 μM) at steady state (near 300 ms). Inhibition by benzamil was at least partially reversible and only observed in Na+ solutions (left panel). K+ currents (right panel) were markedly smaller than Na+ currents.