Adams I, Jones D G
Neurobiol Aging. 1982 Fall;3(3):179-86. doi: 10.1016/0197-4580(82)90038-0.
Ultrastructural observation of the molecular layer of the parietal cortex of rats, aged 3, 6, 10 and 17 months, revealed various atypical synaptic profiles besides typical synapses. The atypical synapses were frequently in the vicinity of hypertrophied astrocytic profiles, and were sometimes completely surrounded by astrocytic processes. The presynaptic terminal contained either no vesicles or a few small distorted vesicles. Vacant postsynaptic terminals were occasionally seen. The total surface area of astrocytic profiles and the numbers of atypical synapses increased significantly between 3 and 10 months. The astrocytic acquisition of degenerating terminals was repeatedly observed over this period. Since there was no decrease in total synaptic number at this age, the astrocytic phenomenon may represent a stage in a continuous cycle of synaptic loss and replacement in the normal brain. By 17 months, when total synapse numbers decrease, synaptic replacement may be less than optimal.
对3、6、10和17月龄大鼠顶叶皮质分子层进行超微结构观察，发现除典型突触外，还有各种非典型突触形态。非典型突触常位于肥大星形胶质细胞形态附近，有时完全被星形胶质细胞突起包围。突触前终末要么不含囊泡，要么含有一些小的变形囊泡。偶尔可见空的突触后终末。在3至10个月期间，星形胶质细胞形态的总表面积和非典型突触的数量显著增加。在此期间反复观察到星形胶质细胞对退化终末的摄取。由于这个年龄段突触总数没有减少，星形胶质细胞现象可能代表正常大脑中突触丧失和替代连续循环中的一个阶段。到17个月时，当突触总数减少时，突触替代可能不太理想。
