Liu, Huan

The adult rodent olfactory system provides an excellent model for the study of the
developing nervous system due to its constant integration of new neurons and
establishment of new synapses throughout life. This allows for adaptive structural
responses to sensory experience that continuously shape functional circuits to fit the
behavioral needs of the animal. The cellular mechanisms underlying the anatomical
plasticity of the adult olfactory system are not well understood, but neurotrophins, long
recognized as crucial to the early development of neuronal circuits, are attractive
candidate molecules in this capacity. Brain-derived neurotrophic factor (BDNF) and
nerve growth factor (NGF), two members of the neurotrophin family, have received
attention in terms of their anatomical distribution and physiological functions in the olfactory system.

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.