*4.11. Electrophysiology*

iPSC-derived neurons cultured on coverslips were transferred to the recording chamber and held down with a small piece of platinum wire [**?** ]. The coverslip was constantly perfused with carbonated artificial cerebral spinal fluid (in mM: 119 NaCl, 2.5 KCl, 1.3 MgSO4, 2.5 CaCl2, 26 NaHCO3, 1.25 NaH2PO4 and 11 glucose; pH ~7.4) at 34 ◦C. Recording pipettes were filled with intracellular solution (in mM: 122.5 potassium gluconate, 12.5 KCl, 10 HEPES, 0.2 EGTA, 2.0 MgATP, 0.3 Na2-GTP, 8.0 NaCl; pH ~7.3) and had a resistance of 4–12 MΩ. Target cells were visualized using a water immersion objective (Olympus, 40×), and whole-cell patch clamp recordings were performed with a HEKA double patch clamp EPC10 amplifier using Patch Master for data acquisition. Voltage and current clamp recordings were used for the electrophysiological characterization. Sodium and potassium currents were evoked by a series of 200 ms long voltage steps (from −70 to +40 mV in 10 mV steps) and inhibited with 1 μM TTX and 10 mM TEA, respectively. Series of current steps (0–200 pA in 10 pA steps) and current ramps from 0–300 pA were performed to determine the cells' ability to generate action potentials. Data were analyzed offline with FitMaster and IgorPro. At least nine cells of each condition were analyzed.
