ClC-1 current is similar in FDB fibers from 4-mo-old mice before and after formamide detubulation in paired experiments, despite a significant reduction in membrane capacitance. (A) Families of 9-AC–sensitive ClC-1 currents recorded from a representative FDB fiber from a 4-mo-old mouse before (black) and after (red) formamide addition and withdrawal. (B) Capacitative currents elicited by a depolarization from +90 to +100 mV before (solid black line) and after (solid red line) formamide addition and withdrawal for the fiber shown in A. Total cell capacitance for this fiber was reduced from 2,073 to 815 pF after formamide addition and withdrawal. (C) Average voltage dependence of steady-state ClC-1 currents recorded from FDB fibers from 4-mo-old mice before (filled symbols) and after (open symbols) detubulation. (D) Average membrane capacitance was significantly reduced 59.2 ± 0.1% (n = 4) in FDB fibers from 4-mo-old mice after formamide addition and withdrawal. Data are presented as mean ± SEM (n = 4).