Defining the role of GABA in cortical development

Of the many signals in the developing nervous system, GABA (gamma-aminobutyric acid) has been shown to be one of the earliest neurotransmitters present. Unlike in the adult, where this transmitter acts synaptically to inhibit neurons, during development, GABA can depolarize progenitor cells and their progeny due to their high intracellular chloride concentration. This early form of GABA signalling may provide the main excitatory drive for the immature cortical network and play a central role in regulating cortical development. Many features of GABA signalling are conserved in different species and are recapitulated during neurogenesis in the adult brain, demonstrating the importance of this versatile molecule in driving cortical formation. Here, we present recent evidence supporting the multiple functions of GABA during embryonic development and adult neurogenesis, from regulating progenitor proliferation to influencing the migration and maturation of newborn neurons.