confirm the presence of functional synapses, we assessed spontaneous activity in the presence of the voltage-gated sodium channel antagonist TTX (Fig 4E). We observed that a proportion of the spontaneous events were blocked by the GABAA receptor antagonist bicuculline. Subsequent application of AMPA/NMDA receptor antagonists AP5 and DNQX blocked all remaining synaptic transmission confirming that these cultures contain both GABAergic and glutamatergic neuronal activity. To test network connectivity of the differentiated neurons, we applied local field stimulation, which elicited synchronized postsynaptic currents (Fig 4F). Hence, the majority of these hPSC-derived neurons produces action potentials and show synaptic responses.
