Fig. 4.

Onset of and recovery from chloroquine block of D172N Kir2.1 current is voltage-dependent. A, Representative current traces recorded in inside-out patches elicited by voltage steps to +80, +70 and +60 mV in presence of 10 µM chloroquine. Lines representing monoexponential fits to data are superimposed over raw current traces. B, The time constants of chloroquine block (τ) were derived by fitting current traces (as in A) to a monoexponential function. The rate constant of block (1/τ) is plotted vs. chloroquine concentration for various voltages. C. D172N current traces recorded in whole-cell configuration (4 mM external K⁺) elicited by hyper-polarizing voltage steps between −120 and −100 mV in the presence of 10 µM chloroquine. D. The time constants of chloroquine unblock (τ unblock) were determined by monoexponential fits to D172N Kir2.1 current elicited by hyperpolarizing voltage steps to membrane potentials negative to the reversal potential for potassium in 4 mM external K⁺ (whole-cell configuration) and 150 mM symmetrical K⁺ (excised inside-out patches). Data represent the mean ± SEM of 4 cells.