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Original Article

Exp Neurobiol 2018; 27(2): 94-102

Published online April 30, 2018

© The Korean Society for Brain and Neural Sciences

Odor Enrichment Increases Hippocampal Neuron Numbers in Mouse

Zoltán Rusznák1#, Gulgun Sengul2, George Paxinos1,3, Woojin Scott Kim1,3† and YuHong Fu1,3†*

1Neuroscience Research Australia, Sydney, NSW 2031, Australia 2Department of Anatomy, School of Medicine, Ege University, Bornova, Izmir 35100, Turkey 3School of Medical Sciences, University of New South Wales, Sydney, NSW 2052, Australia

Correspondence to: *To whom correspondence should be addressed.
TEL: 61-2-93510672
Equal senior authors.
#Present address: Australian Catholic University, Canberra Campus, ACT 2602, Australia.

Received: February 19, 2018; Revised: April 3, 2018; Accepted: April 3, 2018

The hippocampus and olfactory bulb incorporate new neurons migrating from neurogenic regions in the brain. Hippocampal atrophy is evident in numerous neurodegenerative disorders, and altered hippocampal neurogenesis is an early pathological event in Alzheimer's disease. We hypothesized that hippocampal neurogenesis is affected by olfactory stimuli through the neural pathway of olfaction-related memory. In this study, we exposed mice to novel pleasant odors for three weeks and then assessed the number of neurons, non-neuronal cells (mainly glia) and proliferating cells in the hippocampus and olfactory bulb, using the isotropic fractionator method. We found that the odor enrichment significantly increased the neuronal cell numbers in the hippocampus, and promoted cell proliferation and neurogenesis in the olfactory bulb. In contrast, the glial cell numbers remained unchanged in both of the regions. Our results suggest that exposure to novel odor stimuli promotes hippocampal neurogenesis and support the idea that enriched environments may delay the onset or slow down the progression of neurodegenerative disorders.

Graphical Abstract

Keywords: hippocampus, olfactory bulb, neurogenesis, odor stimuli, neurodegeneration, Alzheimer’s disease