(A–E) average basolateral currents elicited as in Figure 3 from apical (red) and basal (blue) IHCs in the presence of different K+ channel blockers to isolate the underlying current components. The control traces (A) are the same as those in Figure 3A and B. (B) The perfusion of linopirdine (80 µM) blocked the inward IK,n in both apical and basal IHCs leaving IK,s and IK,f (apical n = 5, basal n = 7). Linopirdine also removed the outward delayed component in apical cells but not in basal cells. (C) The perfusion of iberiotoxin (IbTx; 60 nM) was used to block the rapidly activating IK,f leaving a current composed of IK,s and IK,n (apical n = 4, basal n = 4). (D) The combination of linopirdine and iberiotoxin (Linop + IbTx) was used to isolate IK,s (apical n = 4, basal n = 4), which was small in apical cells but of a similar size to that in C for basal cells. (E) The isolated IK,n (Linop sensitive) was obtained by subtracting the current in the presence of both linopirdine and IbTx (D) from the current obtained in the presence of IbTx (C). (F) Average tail currents at –124 mV from the linopirdine sensitive current in E for apical and basal IHCs. Only the most negative traces are shown to emphasize the negatively activating component of the linopirdine-sensitive current. (G) Average activation curves for the negatively activating component of the linopirdine-sensitive current from the instantaneous tail current amplitudes in F for apical and basal cells. The inset shows the activation curves up to more positive voltages as in Figure 3H.