Analyses of neuronal replacement in the neuron-depleted olfactory systems in adult mice

New neurons are continuously generated in the olfactory system of adult mice, including olfactory sensory neurons (OSNs) in the olfactory epithelium (OE) and interneurons, produced in the subventricular zone (SVZ) and migrated toward olfactory bulb (OB) along rostral migratory stream (RMS). The present study observed the effects of target neuron loss on the life-span and maturation of adult-born OSNs in the OE and on the proliferation, migration and differentiation of SVZ stem cells in the forebrain after eliminating bulb neurons. We found the life-span of newborn neurons in the absence of synaptic targets was shortened, but the timing of maturation was not delayed. In addition, SVZ cells continued to divide and migrate to the damaged bulb, and the migration of newborn cells in the RMS on the contralateral side was delayed at 2 weeks post-BrdU. Also, the proliferation of cells in dentate gyrus of the hippocampus was not affected by OB damage at 3 weeks post-lesion, though lesion affects occurred in the adult SVZ/RMS.