Bragina T A
Arkh Anat Gistol Embriol. 1983 Oct;85(10):17-24.
Ultrastructure of the proximal part of the axon in the neurons, identified according to a number of morphological signs as pyramidal, has been studied in the layer III of the cat cerebral hemisphere sensomotor cortex. In sections, tangential to the cortical surface, in the initial axonal segment, a submembranous osmophilic layer and fasciculi of microtubules are revealed. On the initial segment spines are found, they contain cysterns resembling by their structure the spine system of the dendritic spines. Axonal terminals revealed along the axonal distribution are in contact both with the axonal trunk and with the spines. Regarding the initial segment, they are presynaptic, contain oval synaptic vesicles and form symmetric axo-axonal synapses only. In transversal sections axonal terminals are detected, arranging on the surface of the initial segment mostly as single ones, in longitudinal sections they are seen as clusters. Analysing the author's data and those from the literature, a conclusion is made that in intact animals the synaptic contacts at the initial segment of the axon are the only form of axo-axonal synapses in the neocortex.
在猫大脑半球感觉运动皮层的Ⅲ层中，对根据多种形态学特征鉴定为锥体细胞的神经元轴突近端的超微结构进行了研究。在与皮质表面相切的切片中，在轴突起始段可观察到膜下嗜锇层和微管束。在起始段发现有棘突，其内含有的囊泡在结构上类似于树突棘的棘突系统。沿轴突分布所揭示的轴突终末既与轴突干接触，也与棘突接触。就起始段而言，它们是突触前的，含有椭圆形突触小泡，仅形成对称的轴 - 轴突突触。在横切面上可检测到轴突终末，它们大多单个地排列在起始段表面，在纵切面上则呈簇状。通过分析作者的数据以及文献中的数据，得出结论：在完整动物中，轴突起始段的突触接触是新皮质中轴 - 轴突突触的唯一形式。
