Estimation of charge movement in probenecid- and carbenoxolone-treated fibers. (A) Examples of charge movement current traces elicited at the onset of depolarizing pulses to values ranging between −50 and +20 mV in a control fiber, in a fiber treated with 1 mM probenecid and in a fiber treated with 100 µM carbenoxolone. (B) Voltage dependence of the charge density in all fibers tested under the indicated conditions. Insets show corresponding mean (±SD) values. Data are from the same fibers as in Fig. 1 (left) and Fig. 2 (right).