Extracellular field potential recordings

Hippocampal slices from tissue harvested on P35 were prepared for electrophysiological studies. Field evoked postsynaptic potentials (fEPSPs) were recorded in the cornu ammonis 1 (CA1) region. Brain slices were placed in a recording chamber and perfused (1.5-2.0 mL/min) with artificial cerebrospinal fluid (ACSF), which was bubbled with 95%O₂/5%CO₂. ACSF-filled theta-glass stimulating pipettes and recording pipettes were put in Schaffer collaterals and the CA1 region accordingly. The distance between the stimulating and recording electrodes was 400-500 μm. fEPSPs were elicited once every 30 s and recorded at 10 kHz (Molecular Devices, USA). Input/output curves were created, and high frequency stimulation (HFS, 100 Hz) was adjusted to evoke 50-60% of the maximum fEPSP. To induce long-term potentiation (LTP), HFS was applied. The fEPSP slope was recorded for 20 min before and 50-60 min after LTP induction. Data were analyzed with Clampfit 10.2 software (Molecular Devices).