Since iN cells exhibit the membrane properties of neurons, we next wanted to assess whether iN cells have the capacity to form functional synapses. To accomplish this we used two independent methods. First, we determined whether iN cells were capable of synaptically integrating into preexisting neural networks. We employed FACS to purify TauEGFP-positive iN cells seven days after infection and re-plated the 5F-iN cells onto neonatal cortical neurons that had been cultured for seven days in vitro. One week after re-plating, we performed patch-clamp recordings from TauEGFP-positive iN cells and observed spontaneous and rhythmic network activity typical of cortical neurons in culture (Fig. 4a–b). Both excitatory and inhibitory postsynaptic currents (EPSCs and IPSCs) could be evoked following electrical stimulation delivered from a concentric electrode placed 100–150 μm away from the patched iN cells, (Fig. 4b–d). In the presence of the AMPA and NMDA receptor channel blockers CNQX and D-APV, spontaneous IPSCs were reliably detected (Fig. 4c, upper panel). Evoked IPSCs could be blocked by further addition of picrotoxin (Fig. 4c, middle panel). Similarly, at a holding potential of −70 mV
