Juraska J M, Fifkova E
J Comp Neurol. 1979 Jan 15;183(2):257-67. doi: 10.1002/cne.901830204.
Synaptic plasticity in response to environmental events has been clearly demonstrated in the visual cortex of the rat, but no detailed data concerning the course of early synaptogenesis in this area are available. In this study, synaptogenesis in the visual cortex of hooded rats at 1, 3, 5, 7 and 10 postnatal days of age (P1-P10) was examined with electron microscopy. The cortex was divided into the molecular layer, the superficial layers (II-IV) and deep layers (V-VI). In the visual cortex at P1, very few synapses are present in the molecular and deep layers and virtually none in the yet undifferentiated layers II-IV that compose the cortical plate at this age. The synapses that are present are axodendritic and often symmetrical with little membrane thickening and few vesicles. Axosomatic synapses were seen as early as P3 but very rarely. There are marked increases in axodendritic synaptic density and maturity with increasing age. By P7 and P10, many synapses appear mature in form and the majority can be classified a symmetrical. Axospinal synapses first appeared at P7 and were more frequent by P10. However, this classification was somewhat uncertain since no spinal apparatus was detected. Rate of synaptogenesis appeared to increase over the ages studied and showed no signs of leveling off except in the deep layers. Synaptic length was extremely variable and did not change systematically with age.
突触可塑性对环境事件的响应已在大鼠视觉皮层中得到明确证实，但该区域早期突触发生过程的详细数据尚无可用。在本研究中，利用电子显微镜检查了出生后1、3、5、7和10日龄（P1 - P10）的带帽大鼠视觉皮层中的突触发生情况。皮层被分为分子层、浅层（II - IV层）和深层（V - VI层）。在P1的视觉皮层中，分子层和深层中存在的突触极少，而在这个年龄构成皮质板的尚未分化的II - IV层中几乎没有突触。存在的突触是轴突 - 树突型的，通常是对称的，膜增厚很少且囊泡较少。轴突 - 胞体型突触最早在P3时可见，但非常罕见。随着年龄增长，轴突 - 树突型突触密度和成熟度显著增加。到P7和P10时，许多突触在形态上显得成熟，并且大多数可归类为对称型。轴突 - 脊髓型突触最早在P7出现，到P10时更为频繁。然而，由于未检测到脊髓结构，这种分类有些不确定。突触发生速率在研究的年龄段中似乎有所增加，除了深层外没有趋于平稳的迹象。突触长度变化极大，且不会随年龄系统性地改变。
