Differential effect of glutamate receptor chronic blockade on mEPSC frequency and amplitude. A,Representative recordings from 15-d-old hippocampal neurons, maintained in control medium or in the presence of 100 μm APV and 20 μm CNQX. B, Distribution of mEPSC frequencies in control and APV–CNQX-treated cells. C, D, Analysis of the average mEPSC frequency (C) and cumulative amplitude distribution (D) in control and treated cells reveals the specific effect of glutamatergic chronic blockade on the frequency, but not the amplitude, of mEPSCs.