FIGURE 4

Increased network excitability, enhanced LTP and impaired inhibition in the LA. (a) Example of a principal cell of the LA and corresponding firing pattern. (b) Response to multi-electrode array (MEA) network stimulation in a voltage-clamped (-80 mV) pyramidal cell, illustrating the typical network activity observed with this stimulation in control and VPA-treated offspring. The percentage of cells showing persistent reverberant activity is higher in treated (15 out of 18 cells) than in control rats (10 out of 21 cells). Among the cells showing this activity, the frequency of reverberant events is higher in treated than in control rats. (c) LTP is enhanced in treated rats. The left graph displays an example of the response amplitudes to extracellular stimulation before and after the pairing protocol (represented by the gray bar), and the middle graph depicts mean amplitudes before and after pairing. The bar graph represents the percentage increase in response amplitude after the pairing for control (n=15) and treated (n=10) rats. (d) The left graph shows a scheme of MEA stimulation with 16 electrodes (50 Hz Poisson train, 300 ms) in principal cells of the LA. The right graphs display the inhibitory response curve of principal cells voltage clamped at +10 mV to MEA stimulation with increasing amplitude. In the upper left corner, the typical response of a single cell is shown. The total area below the curve (charge) is measured for a series of different stimulation intensities. The inhibitory charge generated for all intensities is significantly smaller in the VPA-treated animals. Data show meanSEM (^* p<0.05; ^** p<0.01).