Deficits of peripheral olfactory inputs reduce cell proliferation in the adult subventricular and subgranular zones.

Constitutive adult neurogenesis mainly occurs in the subgranular zone (SGZ) and subventricular zone (SVZ) of the mammalian brain. Intrinsic and extrinsic factors regulate adult neurogenesis processes including cell proliferation, migration, integration and neural survival. The potential contribution of olfactory sensory input to the regulation of adult neurogenesis, especially neurogenesis in the dentate gyrus, however, is not well studied. In the present study, we examined the effects of deficits in the peripheral olfactory inputs on cell proliferation in the adult SGZ and SVZ. With an anosmic model produced by ZnSO4 irrigation of the olfactory epithelium, we found that in the adult SVZ and SGZ the numbers of both BrdU labeled cells and doublecortin labeled cells (immature neurons) were significantly decreased, whereas the number of adult stem cells was not significantly altered. These results suggested that olfactory sensory input may play roles in regulating adult neurogenesis.