Figure 4.

Quantal currents mediated by AMPA receptors develop similarly in control and VPA cortex. A, Examples of voltage-clamp recordings of spontaneous excitatory currents in control and VPA neurons at P9, P16, and P30. B, Cumulative histograms of mEPSC amplitudes, constructed by randomly selecting 50 events from every recording. Data from control and VPA animals have been grouped into three age ranges: P8–P10 (n = 5 control; n = 5 VPA), P15–P17 (n = 6 control; n = 8 VPA), P29–P30 (n = 4 control; n = 4 VPA). On average, four neurons were recorded per animal. A Kolmogorov–Smirnov test (bin size = 2.5 pA) indicates that the amplitude distribution does not differ between conditions at any age (p > 0.2 for all groups). C, In both control and VPA neurons, mEPSC frequency increased and mEPSC amplitude decreased over the course of postnatal development. Plotted are average amplitudes and frequencies from animals grouped into the same age ranges as in B. Vertical error bars are SEM. VPA exposure was not a significant effect. D, Average (peak-scaled) mEPSC waveforms over development. Control and VPA waveforms from each age group have been overlaid. Rise and decay times did not differ significantly at any age.