Age-related Changes of Doublecortin Positive Cells in the Olfactory Bulb of the Rat

Yeo, Seung Geun; Shim, Hyun Joon; Yoon, Sang Won; Kwon, Soon Uk; Park, Kyung Hoon; Huh, Young Buhm; Cha, Chang Il; Cho, Joong Saeng

Abstract

BACKGROUND AND OBJECTIVES: It is well-established that neurogenesis continues to occur during life in the restricted brain areas, such as the glomerular and granule cell layers of the olfactory bulb. Doublecortin is a protein required for neuronal migration in the developing brian and olfactrory bulb, and is expressed in postmitotic migrating and differentiating neurons during embryonic and postnatal development periods. We investigated age-related changes of doublecortin positive cells in the olfactory bulb of aged rat compared with new born rat. MATERIALS AND METHOD: Four months old (control group, n=7) and 24 months old (aged group, n=7) male Fischer 344 rats were used in this study. Olfactory bulbs of the rats were cut into 40 micro m-thick coronal sections and immunostained. We counted the doublecortin positive cells and neurofibrils, and measured the optical density of doublecortin by layer. We compared the results between the aged group and the control group.
RESULTS
In the olfactory bulbs of aged group, we observed less doublecortin positive cells, neurofibrils and lower optical density than the control group. Doublecortin is expressed during life in migratory neuroblasts of the olfactory bulb of the rats. This expression is reduced in the aged group and the reduced degree is variable according to the layer.
CONCLUSION
Age-related changes of the olfactory bulb are associated with the reduction of postnatal neurogenesis, especially during the migration and differentiaion stages. This changes result in reduction of interneurons of the olfactory bulb, and may be responsible for the decreased olfactory function.