Whole-cell recordings were performed at RT with borosilicate glass pipettes (3.5–6.5 mOhm) filled with 125 mM K+-gluconic acid, 10 mM NaCl, 4.6 mM MgCl2, 4 mM K2-ATP, 15mM creatine phosphate, 10U/ ml phosphocreatine kinase and 1mM EGTA (pH 7.30). External solution contained the following (in mM): 10 HEPES, 10 Glucose, 140 NaCl, 2.4 KCl, 4 MgCl2 and 4 CaCl2 (pH = 7.30, 300 mOsmol). Recording were acquired with an Axopatch 200A amplifier (Molecular Devices), Digidata 1322A and Clampex 9.0 software (Molecular Devices). Local field stimulation (2 mA, 1 ms) was applied with a bipolar concentric electrode placed in the vicinity of the patched neuron. Offline analysis was performed using Clampfit v9.0 (Axon Instruments) and Mini Analysis Program v6.0 (Synaptosoft).
