Cells were incubated at room temperature (25 ± 1 °C) in artificial cerebral spinal fluid (containing, in mM: 126 NaCl, 26 NaHCO3, 10 D-glucose, 2.5 KCl, 2 CaCl2, 2 MgCl2 and 1.25 NaH2PO4 pH 7.4) that was oxygenated with 95% O2 and 5% CO2. RFP-labeled cells were visualized with an IR-DIC microscope (Nikon Eclipse FN-1 microscope, 40X water objective). Whole-cell recordings were obtained with borosilicate microelectrodes (4–8 MΩ) pulled with an electrode puller that were filled with internal solution containing (in mM): 4 KCl, 126 K-gluconate, 10 HEPES, 0.3 Na2-ATP, 4 Mg-GTP, 10 phosphocreatine, pH 7.3, 290–310 mOsm. Eletrophysiological recordings were made with an amplifier (Axon MultiClamp 700B, Molecular Devices), signals were filtered at 3 kHz (low pass) and digitized at 20-kHz sampling frequency (DigiData 1550 A, Molecular Devices), and acquired and analyzed with pClamp10 (Molecular Devices). Neurons were first recorded in current-clamp mode, and the responses to 1 second current steps (−10 pA, 2 pA, or 3 pA steps) were recorded to determine the input resistance of the cells. Resting membrane potential (RMP) was not corrected for a liquid
