Recordings were performed from MEF- and tail cell-derived iN cells at 8, 12 and 20 days after viral infection, or 7–13 days after co-culturing with cortical neurons. Spontaneous or evoked synaptic responses were recorded in the whole-cell voltage-clamp mode. Evoked synaptic responses were triggered by 1 ms current injection through a local extracellular electrode (FHC concentric bipolar electrode, Catalogue No. CBAEC75) with a Model 2100 Isolated Pulse Stimulator (A-M Systems, Inc.), and recorded in whole-cell mode using a Multiclamp 700B amplifier (Molecular Devices, Inc.) 37. Data were digitized at 10 kHz with a 2 kHz low-pass filter. The whole-cell pipette solution for synaptic current recordings contained (in mM): CsCl 135, HEPES 10, EGTA 1, Mg-ATP 4, Na4GTP 0.4, and QX-314 10, pH 7.4. The bath solution contained (in mM): NaCl 140, KCl 5, CaCl2 2, MgCl2 0.8, HEPES 10, and glucose 10, pH 7.4. IPSCs were pharmacologically isolated by addition of 50 μM D-AP5 and 20 μM CNQX to the bath solution. EPSCs were pharmacologically isolated by addition of 30 μM picrotoxin and 50 μM D-APV. Data were analyzed using
