Abstract
pocampal aging process. This was done by investigating the morphological structure of the hippocampus, which plays an important role in learning and memory function throughout life.
Methods: Senescence accelerated mouse prone 8//Ymi (SAMP8//Ymi) at 2 months old, which were established as a murine model of aging with defect in learning and memory, were used in this study. Thirty male SAMP 8//Ymi at 2 months old were divided equally into 6 groups. Three groups were kept until 3 (young adult), 5 (middle age), and 8 (old age) months old (normal condition). The remaining three groups, in which their maxillary molar teeth were extracted at 2 months old, were kept until 3, 5, and 8 months old (molarless condition). When they reached the above-mentioned ages, their brains were rapidly removed from the skull, fixed in 10% buffered neutral formalin and processed routinely for paraffin embedding. The coronal sections, 6 Jim thick, cut at the hippocampal level, were stained with Nissl staining. We measured the number of pyramidal cells and the area of single cells within a defined frame in the hippocampal CA3 field.
Results: The mice with molar teeth at 8 months old showed a significant decrease in the number of pyramidal cells and area of single cells compared with the mice with molar teeth at 3 and 5 months old. The mice without molar teeth at 5 and 8 months old showed a significant decrease in the number and size of pyramidal cells compared with the mice without molar teeth at 3 months old. The mice without molar teeth showed a significant decrease in the number of pyramidal cells and area of single cells compared with the mice with molar teeth at 5 months old. However, there is no significant difference at 3 and 8 months old between the above two groups.
Conclusions: In SAMP 8//Ymi, molar teeth loss accelerated an age-related decrease in the number and size of hippocampal CA3 pyramidal cells. Thus it was suggested from the present study that molar teeth loss might play an important role in the morphological changes of the brain as a result of aging.
