mEPSC recordings

For spontaneous mEPSC recordings, neurons were voltage clamped to −70 mV in standard ACSF containing tetrodotoxin (TTX) (0.2 μm), APV (50 μm), and PTX (25 μm) to block action potentials, NMDA receptors, and GABA receptors using a Cs-methanesufonate-based internal solution containing 115 mm Cs-methanesulfonate, 10 mm HEPES, 10 mm BAPTA.4Cs, 5.37 mm biocytin, 2 mm QX-314 Cl, 1.5 mm MgCl₂, 1 mm EGTA, 10 mm Na₂-phosphocreatine, 4 mm ATP-Mg, and 0.3 mm GTP-Na, with sucrose added to bring osmolarity to 295 mOsm and CsOH added to bring pH to 7.35, in pipettes with resistance between 4 and 8 mΩ. 30 s traces were obtained every minute for 5 min. mEPSC event inclusion criteria included rise times <2 ms and amplitudes >6 pA. Neurons were excluded from analysis if they displayed Rs > 20 MΩ, Vm > −50 mV, or Rin < 80 MΩ.