猫嗅球外丛层和僧帽细胞层年龄相关形态学变化

分别用Nissl法及免疫组织化学ABC法标记青、老年猫嗅球中嗅觉二级神经元和外丛层胶质细胞,显微镜下观察其分布并计数,对嗅觉二级神经元胞体直径和外丛层厚度进行测量,比较其年龄相关性变化,研究神经元与胶质细胞之间的关系,探讨老年性嗅觉功能衰退的相关神经机理。结果显示,老年猫嗅觉二级神经元胞体直径和分布密度均有不同程度的显著性下降(P<0.05);外丛层厚度变化不明显(P>0.05);外丛层胶质细胞特别是星形胶质细胞显著性增生(P<0.05)。表明在衰老过程中嗅觉二级神经元有丢失,并呈现功能下降,可能是老年性嗅觉功能衰退的原因之一。同时外丛层胶质细胞增生以进一步保护神经元,延缓其衰老。

Age-related Morphological Changes of External Plexiform and Mitral Cell Layer in the Olfactory Bulb of Cats

To investigate the function of secondary neurons in the olfactory bulb(OB) of young adult and old cats,we applied Nissl staining to display secondary olfactory neurons,and immunostaining of glial fibrillary acid protein(GFAP) and S100 protein to show astrocytes and glial cells respectively in the external plexiform layer(EPL) of OB.Under the microscope,secondary olfactory neurons,GFAP-immunoreactive(GFAP-IR) cells and S100-immunoreactive(S100-IR) cells were observed and quantified.Furthermore,the diameter of secondary olfactory neurons and the thickness of EPL were measured.Compared to the young cats,the number of secondary olfactory neurons in old cats declined significantly(P<0.05);the thickness of EPL had no evident difference(P>0.05);and the density of S100-IR cells especially GFAP-IR cells in the EPL of old cats was obviously higher(P<0.05).Neuron loss was accompanied with glial hyperplasia during senescence.In addition,the diameter of secondary olfactory neurons in old cats decreased significantly(P<0.05),revealing functional degeneration of aged neurons in the OB.Loss of secondary olfactory neurons may be an important reason for aged olfactory degeneration,and glial enhancement in old individuals may offer nutrition to surviving neurons to postphone their further aging.