Figure 3: NMDA receptors mediate spontaneous activity but not fEPSPs. Blocking (MK801) or enhancing (low-Mg2+ ACSF) NMDAR function did not influence fEPSPs (a). Right panel shows representative fEPSPs before (grey) and after (black) treatment. Bar graphs show the average of the fEPSPs amplitudes of the 25–30 min period after treatment (b). In contrast, MK801 dose dependently reduced spiking frequency and low Mg2+ ACSF enhanced firing rate (untreated versus MK801 in 25 μM: and untreated versus low Mg2+ ACSF: ) (c). Inset shows representative spike trains. Error bars show SEM; , .