Whole-cell patch-clamp recordings.

Whole-cell electrophysiology recordings were performed as previously described using the following solutions ²⁶. Extracellular recording buffer contained (in mM): 128 NaCl, 30 glucose, 25 HEPES, 5 KCl, 2 CaCl₂, and 1 MgCl₂ (pH 7.3). For current- and voltage-clamp measurements, pipettes were filled with (in mM): 135 KGluconate, 10 Tris-phosphocreatine, 10 HEPES, 5 EGTA, 4 MgATP, and 0.5 Na₂GTP (pH 7.3). Patch pipettes were fabricated from borosilicate glass (N51A, King Precision Glass, Inc.) to a resistance of 2–5 MΩ. Current signals were recorded with either an Axopatch 200B (Molecular Devices) or a Multiclamp 700A amplifier (Molecular Devices) and were filtered at 2 kHz using a built in Bessel filter and digitized at 10 kHz. Voltage signals were filtered at 2kHz and digitized at 10kHz. Data was acquired and analyzed using Axograph on a Dell PC (Windows 7). For voltage clamp recordings, cells were held at −70 mV for sodium/potassium currents and sEPSCs, and 0 mV for sIPSCs. After recording a ramp protocol (−110 to 110 mV, 0.22 mV/s) for each neuron in voltage clamp, the recording configuration was switched to current clamp and a series of APs (20 episodes) was elicited at 0.5 Hz with a square current injection that was increased by 10 pA every episode. Calculation of dV/dT maximum and minimum was set as the maximum slope for the ascending and descending phases with three regression points per maximum slope.