between EPSCs and IPSCs containing: 145 mM K+ gluconate, 0.1 mM CaCl2, 2.5 mM MgCl2, 10 mM HEPES, 0.2 mM EGTA, 4 mM Na+ phosphocreatine. Cl− reversal was calculated to be at −91 mV according to the Nernst equation. A high Cl− internal solution was used to measure EPSCs in a subset of unfused hSS containing: 135 mM CsCl, 10 mM HEPES, 10 mM EGTA, 3 mM MgATP, 0.3 mM GTP. The Cl− reversal potential was calculated to be 0 mV according to the Nernst equation. IPSCs were blocked by application of the GABAA receptor antagonist gabazine (10 μM, Abcam), which was added to superfused aCSF. EPSCs were blocked by application of the glutamate receptor antagonist kynurenic acid (1 mM, Abcam), which was added to superfused aCSF. Electrical simulation was delivered using a bipolar tungsten electrode (FHS) placed 200–400 μM away from a recorded neuron. Stimulations were delivered to slices for 0.1 ms at 300 μV and separated by at least 10 s. Inward EPSCs and outward IPSPs were recorded by filling the patch pipette with a low chloride internal solution (ECl–= −90 mV) and holding the cell at −40 mV, which is near the midpoint between ECl– and EK+/Na+.
