Jones D G, Calverley R K
Department of Anatomy, University of Otago, Dunedin, New Zealand.
Brain Res. 1991 Aug 16;556(2):247-58. doi: 10.1016/0006-8993(91)90312-j.
Perforated and non-perforated synapses in the molecular layer of rat parietal cortex have been assessed morphologically and quantitatively using three-dimensional reconstructions of the postsynaptic terminal. Perforated synapses were analyzed at nine ages, ranging from 0.5 to 22 months of age, and non-perforated synapses at three ages--0.5, 12, and 22 months. Examination of the reconstructions shows that perforated synapses increase in size and complexity with increasing age. This increasing complexity is reflected in a break-up of the postsynaptic density, which is punctuated by larger, branched perforations. In the most extreme cases the result is the appearance of isolated islands of postsynaptic density separated by, and also surrounded by, a synaptic contact zone. Spinules are especially prominent at around 12 months of age in perforated synapses, and the overall negative curvature of the young junctions is replaced by positively curved junctions from 4 months onwards. The non-perforated synapses are relatively small and show few changes with increasing age. Using the measurement option in the reconstruction program, the following trends emerged. All parameters of perforated synapses increased in size with increasing age, whereas the corresponding parameters of non-perforated synapses remained relatively unchanged over this age range. In addition, the percentage of the synaptic contact zone surface area occupied by the postsynaptic density decreased with increasing age in perforated synapses, but increased in non-perforated synapses. The total postsynaptic density surface area of non-perforated synapses per unit volume of molecular layer was double that of perforated synapses at 0.5 months, but the situation was reversed at 12 months. This parameter was similar in the 2 populations at 22 months. This suggests that perforated synapses contribute more to the total surface area of the postsynaptic density in mid- to late-adulthood than do non-perforated synapses, despite non-perforated synapses outnumbering perforated by 2-3:1 at these ages. These data provide more specific evidence that perforated and non-perforated synapses constitute separate synaptic populations from early in development, and that perforated synapses are responsible for the maintenance of neuronal postsynaptic density surface area from mid-adulthood onwards.
利用突触后终末的三维重建技术，对大鼠顶叶皮质分子层中的穿孔型和非穿孔型突触进行了形态学和定量分析。对穿孔型突触在0.5至22个月龄的9个年龄段进行了分析，对非穿孔型突触在0.5、12和22个月龄这3个年龄段进行了分析。对重建结果的检查表明，穿孔型突触的大小和复杂性随着年龄的增长而增加。这种不断增加的复杂性表现为突触后致密物的分解，其被更大的、分支状的穿孔所打断。在最极端的情况下，结果是出现了被突触接触区分隔且周围也被其包围的孤立的突触后致密物岛。棘状突起在穿孔型突触约12个月龄时尤为突出，并且从4个月龄起，年轻突触的整体负曲率被正曲率的突触所取代。非穿孔型突触相对较小，并且随着年龄的增长变化不大。利用重建程序中的测量选项，出现了以下趋势。穿孔型突触的所有参数随着年龄的增长而增大，而非穿孔型突触的相应参数在这个年龄范围内保持相对不变。此外，穿孔型突触中突触后致密物所占突触接触区表面积的百分比随着年龄的增长而降低，而非穿孔型突触中则增加。在0.5个月时，分子层每单位体积中非穿孔型突触的突触后致密物总表面积是穿孔型突触的两倍，但在12个月时情况相反。在22个月时，这两个群体的这个参数相似。这表明，尽管在这些年龄段非穿孔型突触的数量比穿孔型突触多2至3倍，但在成年中期到晚期，穿孔型突触对突触后致密物的总表面积贡献更大。这些数据提供了更具体的证据，表明穿孔型和非穿孔型突触从发育早期就构成了不同的突触群体，并且穿孔型突触从成年中期起负责维持神经元突触后致密物的表面积。
