Effect of inhibitors of the ERK1/2 pathway. A, Representative traces from two individual extracellular electrodes in control conditions (left) and in the presence of 50 μM PD98059 (right). B, Corresponding network firing rate computed with a bin width of 25 ms, in normal conditions (left) and in the presence of 50 μM PD98059 (right) showing a depression of the spontaneous electrical activity by PD98059. Dotted line indicates zero spike. C, The evoked activity is still potentiated when the ERK1/2 pathway was blocked before GabT (see Results). Dashed line corresponds to potentiation of the evoked activity without blocking the ERK1/2 pathway before GabT. Data for PD98059 (50 μM; n = 3) and U0126 (20 μM; n = 3) were pooled together as they affected network properties in a similar way. D, Changes of gene expression occurring 1.5 h after GabT measured by Real-Time PCR for Egr1, Egr2, Egr3, Nr4a1, Bdnf, Homer1a and Arc in the presence of gabazine and PD98059 (gray bars) relative to normalized expression in the presence of gabazine alone (black bar).