Fernández and Raineteau the Bordey’s lab and others (Melchiorri et al., 2007; Platel et al., 2010a), this work demonstrates that it is the differential expression of distinct receptors that will mediate varied activities of glutamate on cellular processes as diverse as prolifera- tion, migration and survival throughout SVZ neurogenesis. These findings are significant for several reasons. First, they identify a novel mecha- nism which, together with the modulation of neural progenitor proliferation in the SVZ and the differential survival of new- born neurons in the OB, might contribute to the tight regulation of neurogenesis in the mammalian forebrain. A wide variety of experimental/environmental manipula- tions have been shown to modulate OB neu- rogenesis (Ma et al., 2009). In this context, it will be interesting to assess if stimuli that increase or decrease OB neurogenesis also regulate glutamate release by RMS astro- cytes, and to identify the possible mecha- nisms mediating these changes. This study might also be of relevance in the context of forebrain repair by endogenous neural stem/progenitor cells. Numerous studies have shown the migra- tion of SVZ-generated neuroblasts to sites of forebrain injury. A striking example is the sustained neuroblast migration to the striatum after stroke. This process persists for several months, but its contribution to repair is tempered by the poor survival of the recruited neuroblasts (Thored et al., 2006). It would be interesting to examine the involve- ment of NMDARs in mediating this weak survival. RMS astrocytes might differ from astrocytes (quiescent or reactive) in other brain regions (intact or denervated), in their capacity to release glutamate and therefore to promote the survival of neuroblasts that are recruited to sites of injury. Thus, although it is well known that astrocytes from various brain regions show calcium transients and might release glutamate in response to neu- ronal activity (Agulhon et al., 2008), recent research has questioned the significance of this process in the context of synaptic NMDAR activation (Agulhon et al., 2010). In conclusion, this work changes our view of the RMS as a passive pathway for neurob- last migration. It highlights that the RMS is a highly specialized forebrain compartment, comparable to the SVZ neurogenic niche, where astrocytes play an intricate role in modulating survival of migrating neurob- lasts. Finally, taken together with previous work from the same laboratory and others, these findings illustrate how amino-acid neurotransmitters control multiple steps of a complex cellular differentiation process in the postnatal forebrain. RRfescne Agulhon, C., Fiacco, T. A., and McCarthy, K. D. (2010). Hippocampal short- and long-term plasticity are not modulated by astrocyte Ca2+ signaling. Science 327, 1250–1254. Agulhon, C., Petravicz, J., McMullen, A. B., Sweger, E. J., Minton,S.K.,Taves,S.R.,Casper,K.B.,Fiacco,T.A.,and McCarthy, K. D. (2008). What is the role of astrocyte calcium in neurophysiology? Neuron 59, 932–946. Alonso, M., Viollet, C., Gabellec, M. M., Meas-Yedid, V., Olivo-Marin, J. C., and Lledo, P. M. (2006). Olfactory discrimination learning increases the survival of adult-born neurons in the olfactory bulb. J. Neurosci. 26, 10508–10513. Fiacco,T.A.,Agulhon,C.,Taves,S.R.,Petravicz,J.,Casper, K. B., Dong, X., Chen, J., and McCarthy, K. D. (2007). 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Control of neuroblast production and migration by converging GABA and glutamate signals in the postnatal fore- brain. J. Physiol. 586, 3739–3743. Platel, J. C., Stamboulian, S., Nguyen, I., and Bordey, A. (2010a).Neurotransmitter signaling in postnatal neu- rogenesis: the first leg. Brain Res. Rev. 63, 60–71. Platel,J.C.,Dave,K.A.,Gordon,V.,Lacar,B.,Rubio,M.E., and Bordey,A.(2010b).NMDA receptors activated by subventricular zone astrocytic glutamate are critical for neuroblast survival prior to entering a synaptic network. Neuron 65, 859–872. Thored, P., Arvidsson, A., Cacci, E., Ahlenius, H., Kallur, T., Darsalia,V., Ekdahl, C. T., Kokaia, Z., and Lindvall, O. (2006). Persistent production of neurons from adult brain stem cells during recovery after stroke. Stem Cells 24, 739–747. Received: 29 April 2010; paper pending published: 25 May 2010; Accepted: 08 June 2010; published online: 24 June 2010. Citation: Fernández ME and Raineteau O (2010) Excitement keeps your brain cells alive. Front. Neurogenesis 4:46. doi: 10.3389/fnins.2010.00046 This article was submitted to Frontiers in Neurogenesis, a specialty of Frontiers in Neuroscience. Copyright © 2010 Fernández and Raineteau. This is an open-access article subject to an exclusive license agreement between the authors and the Frontiers Research Foundation, which permits unrestricted use, distribution, and reproduc- tion in any medium, provided the original authors and source are credited. Frontiers in Neuroscience | Neurogenesis June 2010 | Volume 4 | Article 46 | 2