Fig. 1.

Bisphenol A (BPA) inhibits compound action potentials (CAPs) recorded from frog sciatic nerve fibers without changing the threshold for CAP generation. (A) BPA at a concentration of 0.5 mM reduces CAP peak amplitudes in a partially reversible manner. Top of figure: recordings of CAPs in the control, at 20 min after exposure to BPA, and 60 min following BPA washout. Bottom of figure: average time course of changes in CAP peak amplitudes following exposure to BPA for 20 min, relative to that before exposure, obtained from four sciatic nerves. In this and subsequent figures, the stimulus strength used to elicit CAPs was one at which a maximal CAP was produced (see below), unless otherwise mentioned; each point with vertical bars represents the mean and S.E.M.; the S.E.M. of a value without a visible vertical bar is smaller than the size of the data point. (B) Comparison of the average time course of CAP peak amplitude reductions produced by BPA at 0.002–0.5 mM, obtained from 24 sciatic nerves. (C) Plot of the peak amplitudes of CAPs, relative to control, recorded from sciatic nerve fibers treated with BPA of various concentrations for 20 min. Each of the data points was obtained from 3 to 6 sciatic nerves. The concentration-response curve was drawn according to the Hill equation (half-maximal inhibitory concentration, IC₅₀=0.31 mM; Hill coefficient, n_H=1.5). (D) Stimulus strength dependence for CAP peak amplitude reduction produced by BPA. The peak amplitudes of CAPs before (open circles) and after exposure to BPA (0.2 mM; closed circles) for 20 min, plotted against the stimulus strength used to elicit the CAP. Insets show recordings of CAPs elicited at 0.32 and 0.50 V in the control (left) and after exposure to BPA for 20 min (right). The solid lines in (B) and (D) were drawn arbitrarily.