Preparation of acute hippocampal slices
For fEPSP recordings and GABA uptake studies, the hippocampus (6-12 weeks-old Sprague-Dawley rats or C57BL/6 mice as specified in results section) were dissected within ice-cold artificial cerebrospinal fluid (aCSF) solution composed of (mM): NaCl 124, KCl 3, NaHCO3 25, NaH2PO4.H2O 1.2, MgSO4 1, CaCl2 2; and glucose monohydrate 10, previously gassed with 95% O2 and 5% CO2, pH 7.4. Slices (400 µm thick for fEPSP recordings or 300 µm thick for GABA uptake studies) were cut perpendicularly to the long axis of the hippocampus with a McIlwain tissue chopper (Campden Instruments) and allowed to recover functionally and energetically for at least 1 hour in a resting chamber filled with the same solution, at room temperature (RT) and continuously gassed. For patch clamp recordings, the slices (300 µM thick from 5-8 weeks old Wistar rats) were cut with a vibratome (Leica VT 1000S, Leica Microsystems) in the ice-cold dissecting solution containing (in mM): sucrose 110; KCl 2.5; CaCl2 0.5; MgCl2 7; NaHCO3 25; NaH2PO4 1.25; glucose monohydrate 7, oxygenated with 95% O2 and 5% CO2, pH 7.4; after dissection, the slices were incubated for 20 minutes at 35°C in aCSF and then transferred to a resting chamber at RT for at least 1 hour before use.