中文摘要：

目的：探讨老年大鼠大脑胼胝体体积及胼胝体额区有髓神经纤维的改变。方法：运用透射电子显微镜和新的体视学方法分别对年轻组、中老年组和老年组雌性Long-Evans大鼠胼胝体体积及胼胝体额区有髓神经纤维进行定量研究。结果：与年轻组比较，中老年和老年的胼胝体体积和胼胝体额区体积均存在显著性降低，胼胝体额区体积的老年性改变出现更早，老年改变程度更大。老年大鼠胼胝体额区有髓神经纤维总体积较年轻大鼠有下降趋势；有髓神经纤维总长度较年轻大鼠下降19．5％，直径在0．4～0．6μm范围的有髓神经纤维长度下降28．1％。结论：胼胝体存在显著性老年萎缩，老年胼胝体额区具有选择易损性，胼胝体额区的老年改变可能与老年大脑额叶功能下降有关。

英文摘要：

Objective： To explore the age-related changes of corpus callosum volume and its myelinated fibers in the frontal region in old＇ rats. Methods ： The total volume of the corpus callosum and the myelinated nerve fibers in the frontal region of corpus callosum among young, middle-aged and old female Long-Evans rats were studied under an electron microscopy and with unbiased stereological techniques. Results： Compared to the young female rats, the total volume of the corpus callosum and the frontal region of the corpus callosum were significantly decreased in the middle-aged and old rats. The age related change in the frontal region of corpus callosum occurred early and was more prominent when compared to entire corpus callosum. There was a trend for the age related decline of the total volume of the myelinated fibers in the frontal region of corpus callosum. The total length of the myelinated fibers in the frontal region of the corpus callosum in old-aged female rats was decreased by 19.5% and that of the myelinated nerve fibers with diameter from 0.4 to 0.6 μm was decreased by 28.1% when compared to the young group. Conclusion： There is age-related atrophy of the corpus caltosum. The frontal region of the corpus callosum is more vulnerable to aging process than other regions of the corpus callosum. The age-related changes of the frontal region of corpus callosum may be related to the decline of frontal lobe functions with aging.