Field excitatory postsynaptic potentials (fEPSPs) recordings
Acute hippocampal slices were individually transferred into a submerged recording chamber over the nylon mesh and continually superfused with gassed aCSF solution at a constant flow (3 mL/min) and temperature (32 °C). Stimulation (rectangular 0.1 ms pulses, once every 15 seconds, S48 Square Pulse Stimulator, Grass Instruments) was delivered through a concentric bipolar electrode placed on Schaffer collateral-commissural fibbers, in the stratum radiatum near the CA3-CA1 border. The stimulus intensity was set to elicit nearly 50% of the maximal response and was maintained throughout the experiment. fEPSPs were recorded through a microelectrode (2–6 MΩ resistance, filled with aCSF), placed in CA1 stratum radiatum , coupled to an Axoclamp 2B amplifier (Axon Instruments) and digitized BNC-2110 (National Instruments). Individual responses were monitored, and averages of 8 consecutive responses were continuously stored on a personal computer with the WinLTP software (Anderson and Collingridge, 2007). Test drugs were added to the superfusing aCSF after obtaining a stable baseline of recordings for at least 15 minutes.