stage, as indicated by incomplete inhibition of neuronal activity by CNQX, an antagonist of AMPA receptors, at the 3-week time point and complete inhibition of activities at the 6-week time point. Finally, previous studies have demonstrated that maturation of new hippocampal granule neurons progress through a GABA-excitatory stage as a result of elevated intracellular chloride concentration, denoting a transient hyperexcitatory phase in the maturation of DG granule neurons (Li et al., 2012). The neurons generated using our differentiation protocol presented spontaneous activity that was inhibited by GABA at both 3 and 6 weeks differentiation. It is conceivable that the GABA excitatory period of development precedes the time points surveyed here and that the neurons have already switched to glutamate-mediated excitatory transmission. However, a progressive increase in GABA sensitivity with maturation is consistent with existing animal studies (Ganguly et al., 2001; Li et al., 2012).
