Figure 4. Gentamicin impairs the Ca²⁺ influx necessary for I_K(ACh) activation.

A, currents recorded using a tail protocol (bottom middle) in control conditions (top middle) or during an ACh100 (top right, filled bar) or ACh100GM30 (top left, open bar) application. The tail protocol is identical to the fast protocol described in Fig. 1C, except that voltage steps were triggered from a V_h of -10 mV; the horizontal bar indicates the timing of pressure-puff application. Net currents triggered by ACh100 (bottom right) or ACh100GM30 (bottom left) during the tail protocol were obtained after subtraction of the control leak currents recorded in between. Current amplitudes reported in B were measured 8 ms after the offset of each voltage step as indicated by the arrows under the corresponding symbols. B, I-V relationships of the tail currents presented in A. Tail current amplitudes triggered during ACh100 (♦) or ACh100GM30 (⋄) application were measured as described in A. Data presented in this figure are from the same cell as illustrated in Fig. 3C–E recorded with internal solution 1. All these effects were reversible and repeated several times.