While the identity of NSCs in the adult brain is not clearly documented, it appears likely that they have many features characteristic of astroglia (Imura et al., 2003; Alvarez-Buylla and Lim, 2004; Liu et al., 2006). Like embryonic radial glia, adult SVZ NSCs have GABAA receptors which limit their proliferation in response to GABA released by neuroblasts, suggesting negative feed-back regulation via non-synaptic GABAergic signaling between neuroblasts and GFAP-expressing NSCs (Liu et al., 2005).