Comparative ultrastructural study of the optic nerves and visual cortices of young (2.5 months) and old (17 months) mice.

The aging optic nerves and visual cortices were studied in mice. Changes in the morphology of neuroglia were evident in the optic nerve but no difference in the numbers of neurotubules or myelin sheaths optic nerve fibers in the aged were observed. Large myelinated fibers, however, begun to degenerate. In the aging visual cortices, a higher proportion of dendrodendritic contacts were present and microglia cells were found to be active.