Early maturation of GABAergic synapses in mouse retinal ganglion cells

This study was aimed to characterize the earliest phases of synapse development in mouse retinal ganglion cells (RGCs) by recording spontaneous postsynaptic currents (PSCs). First PSCs were detected at embryonic day 17 and completely suppressed by bicuculline, demonstrating their GABAergic nature. Starting from postnatal day 3 a small fraction of RGCs had rapidly decaying, most likely glutamatergic currents. The present results suggest that functional GABAergic synapses with RGCs appear before birth and that GABAergic synaptic transmission precedes that of glutamate in the retina. In this early period GABA acts in a depolarizing manner and takes over an excitatory function.