The rostral migratory stream is a neurogenic niche that predominantly engenders periglomerular cells: In vivo evidence in the adult rat brain

In vitro studies support the existence of adult neural stem cells in the rostral migratory stream (RMS). The evidence supporting this possibility in vivo is scarce. We then explore this issue by taking advantage of a rat model in which a physical barrier implanted in the brain interrupted the migration of neuroblasts derived from the SVZ along the RMS at the level of its vertical limb. The presence of local stem cells and neurogenesis were then established by estimating the number of nuclei labeled with bromo-deoxyuridine (BrdU), the number of doublecortin-positive neuroblasts and the existence of cells displaying co-localization of BrdU and Sox-2 immunoreactivity along the RMS, at different time points following barrier implantation. Estimations of the number of the granular and periglomerular neurons integrated into the corresponding layers of the olfactory bulb of implanted rats established that stem cells in the RMS give rise predominantly to periglomerular neurons. Our results then support the notion that the RMS is indeed a region in which neurogenesis is taking place in the adult brain. They also support that the relative location of the neurogenic niche might imprint, at least in some degree, the identity and lineage of the neuroblasts arising from them.