Fig. 6. Rapid, long-lasting depression of synaptic transmission following NMDA exposure. (A) Time course of changes in fEPSP amplitude following a 10 minute bath application of 3 µM NMDA. fEPSP evoked by stimulation of the Schaffer collaterals was recorded extracellularly from the CA1 stratum pyramidale of cultured hippocampal slices. Representative fEPSP recordings at times -10 (1) and 58 (2) are shown in the inset. Arrows indicate stimulation-elicited artifacts. Data are expressed as the percentage of pretreatment fEPSP amplitude; means±s.e.m. of four slices. (B) Reversible NMDA-induced suppression of synaptic transmission. fEPSP was recorded immediately before (pre) or at 0, 1, 24 and 48 hours after 10 minutes exposure to 3 µM NMDA. Data are the means±s.e.m. of seven to eight different slices. *P<0.05, **P<0.01 versus Pre. NMDA induced a rapid, long-lasting decrease in synaptic response, which almost completely recovered after NMDA washout. Recovery time was relatively slow, requiring 48 hours.