• Applied Microscopy
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• v.36 no.2
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• pp.119-130
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• 2006

To investigate the role of myelin-associated glycoprotein (MAG) in the normal aging process, aging-related morphometric and ultrastructural analyses of the MAG-positive (MAG-(+)) oligodendrocytes were carried out in the cerebral cortex of the Sprague-Dawley rats. In the aged rats, the density of MAG-(+) oligodendrocytes was significantly decreased in the cortical layer (IV-VI) compared with that of the adult rats. However, the percentage of medium and dark types of oligodendrocytes was significantly increased by aging. In the aged rats, the mean nuclear area of the MAG-(-) oligodendrocytes was interestingly reduced compared with that of MAG-(+) oligodendrocytes. In addition, MAG immunoreactive products were markedly decreased in the medium-dark type of oligodendroglial cytoplasm and processes, and were scarcely localized in the dark type of oligodendrocytes of the aged rats. These results suggest that degeneration of oligodendrocytes-myelin system by aging is associated with down regulation of MAG, and that may contribute to further understanding of the biology of MAG in the oligodendrocytes-myelin system.