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目的研究大鼠胼胝体中段和压部体积及其内有髓神经纤维的老年改变。方法运用新的体视学方法和透射电镜技术定量研究成年、中年和老年雌性Long-Evans大鼠胼胝体中段和压部的体积、有髓神经纤维的长度密度、总长度、有髓神经纤维的直径。结果胼胝体中段体积在老年组比成年组和中年组分别显著降低21.5%和18.1%,而胼胝体压部体积变化不明显。胼胝体中段和压部有髓神经纤维的长度密度、总长度、平均直径均没有明显的老年改变。老年组大鼠大脑胼胝体中段内直径为0.7～0.8μm的有髓神经纤维总长度比成年组大鼠显著减少3.45km,直径为1.5～1.6μm的有髓神经纤维的总长度比成年组显著增加0.5km。老年组大鼠大脑胼胝体压部内直径为1.2～1.3μm和1.4～1.5μm的有髓神经纤维总长度分别较成年组大鼠显著增加0.123km和0.108km。结论老年大脑胼胝体压部没有发生显著性萎缩。老年大脑胼胝体中段体积显著性下降,胼胝体中段内小直径的有髓神经纤维总长度显著性降低可能是老年胼胝体中段体积显著性下降的重要原因之一。
Objective To study the changes of the volume and the myelinated nerve fibers in the middle part of the corpus callosum and the pressure in rats. Methods The volume and volume density of myelinated nerve fibers in adult and middle-aged and old female Long-Evans rats were measured by using new stereological methods and transmission electron microscopy. The myelinated nerve fibers’ diameter. Results The volume of the corpus callosum was significantly decreased by 21.5% and 18.1% in the aged group compared with the adult group and the middle-aged group, respectively, while the volume of the corpus callosal body did not change significantly. There were no significant changes in the length, mean length and length of the myelinated nerve fibers in the middle and the corpus callosum. The total length of myelinated nerve fibers in the middle of the corpus callosum in the aged group was significantly decreased by 3.45km and the diameter of the myelinated nerve fibers with the diameter of 1.5 ~ 1.6μm was significantly increased than that of the adult group 0.5km. The total length of myelinated nerve fibers with diameter 1.2 ~ 1.3μm and 1.4 ~ 1.5μm in the corpus callosum of the aged rats increased by 0.123km and 0.108km respectively compared with the adult rats. Conclusion There is no significant atrophy of the corpus callosum in the senile brain. The volume of the middle part of the corpus callosum of the aged brain decreased significantly. The significant decrease of the total length of the small diameter myelinated nerve fibers in the middle part of the corpus callosum may be one of the important reasons for the significant decrease of the middle part of the corpus callosum.