Comparison of Ionized Calcium-binding Adapter Molecule 1 Immunoreactivity of the Hippocampal Dentate Gyrus and CA1 Region in Adult and Aged Dogs
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Similarities between age-related changes in the canine and human brain have resulted in the general acceptance of the canine brain as a model of human brain aging. The hippocampus is essentially required for intact cognitive ability and appears to be particularly vulnerable to the aging process. We observed changes in ionized calcium-binding adapter molecule 1 (Iba-1, a microglial marker) immunoreactivity and protein levels in the hippocampal dentate gyrus and CA1 region of adult (2–3 years) and aged (10–12 years) dogs. We also observed the interferon-γ (IFN-γ), a pro-inflammatory cytokine, protein levels in these groups. In the dentate gyrus and CA1 region of the adult dog, Iba-1 immunoreactive microglia were well distributed and their processes were highly ramified. However, in the aged dog, the processes of Iba-1 immunoreactive microglia were hypertrophied in the dentate gyrus. Moreover, Iba-1 protein level in the dentate gyrus in the aged dog was higher than in the adult dog. IFN-γ expression was increased in the dentate gyrus homogenates of aged dogs than adult dogs. In addition, we found that some neurons were positive to Fluoro-Jade B (a marker for neuronal degeneration) in the dentate polymorphic layer, but not in the hippocampal CA1 region in the aged dog. These results suggest that Iba-1 immunoreactive microglia are hypertrophied in the dentate gyrus in the aged dog.
KeywordsAging Dog Hippocampus Microglia Ionized calcium-binding adapter molecule 1
The authors would like to thank Mr. Seok Han, Mr. Seung Uk Lee and Ms. Hyun Sook Kim for their technical help in this study. This work was supported partially by the MRC program of MOST/KOSEF (R13-2005-022-01002-0).
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