al., 2006). Finally, studies have also shown a transition in hippocampal granule neurons from a GABA-excitatory to a GABA-inhibitory state during early maturation as a result of changes in intracellular Cl− concentration due to the upregulation of the KCC2 channel (Ganguly et al., 2001; Li et al., 2012). In our hands, GABA inhibited the network activity of neurons at both 3 and 6 weeks, with greater reduction at the 6-week postdifferentiation, further indicating the maturation of the neuronal population (Figures 4C, 4D, and 4G).
