Tömböl T, Eyre M, Zayats N, Németh A
Department of Anatomy, Histology and Embryology, Semmelweis University, Budapest, Hungary.
Cells Tissues Organs. 2003;175(4):202-22. doi: 10.1159/000074942.
The ramification patterns and terminals of optic fibres in layers 2 and 3 of the optic tectum were studied in Golgi-stained and immunolabelled preparations made from the brains of chicks and pigeons. The different neuronal structures of layers 2 and 3 were also examined. In Golgi preparations, two types of optic fibre were found both in chick and pigeon tectum according to their thickness and terminal branching patterns. The same types of optic fibres were also found to be present in the anterograde tracer experiments after iontophoresis of biotinylated dextran amine into the optic nerve. The varicose terminals of thin fibres mostly terminated on terminal dendritic sections of radiate and pyramidal-like neurons, contacting them on their apical dendrites. The medium-thick fibre terminals in layer 2 mainly established synapses with horizontally extending dendrites, which may therefore be contacts with inhibitory local circuit neurons. The medium-thick optic fibre bushy-like arborisation in layer 3 established synapses with larger dendrites and also stem dendrites. Their terminals formed groups with different dendritic profiles, some of which were partly covered by glial processes, and/or were located among converging dendrites. The presence of these glomerular-like synapses in layer 3 proves that the optic terminals in layer 3 also take part in the transmission of optic impulses to the nucleus rotundus.
在由鸡和鸽的大脑制作的高尔基染色和免疫标记标本中，研究了视顶盖第2层和第3层中视神经纤维的分支模式和终末。还检查了第2层和第3层不同的神经元结构。在高尔基标本中，根据其厚度和终末分支模式，在鸡和鸽的视顶盖中均发现了两种类型的视神经纤维。在将生物素化葡聚糖胺离子导入视神经后的顺行示踪实验中，也发现了相同类型的视神经纤维。细纤维的曲张终末大多终止于放射状和锥体形神经元的终末树突段，与它们的顶端树突相接触。第2层中的中等粗细纤维终末主要与水平延伸的树突建立突触，因此可能是与抑制性局部回路神经元的接触。第3层中中等粗细的视神经纤维呈浓密分支状，与较大的树突以及主干树突建立突触。它们的终末与具有不同树突形态的树突形成群组，其中一些部分被胶质细胞突起覆盖，和/或位于汇聚的树突之间。第3层中这些肾小球样突触的存在证明，第3层中的视神经终末也参与了视冲动向圆核的传递。
