猫后索核内后根初级传入终末与丘脑投射神经元之间的突触联系

THE SYNAPTIC RELATIONSHIP BETWEEN THE PRIMARY AFFERENT TERMINALS AND THE THALAMIC PROJECTION NEURONS IN THE CAT DORSAL COLUMN NUCLEUS

用ＨＲＰ逆行追踪与顺行演变相结合的方法，研究了猫后索核内初级传入终末与丘脑投射神经元之间的突触联系形式。在电镜下可见后东核内有５种突触联系形式：１．溃变轴突终末与ＨＲＰ标记树突形成的轴一树突触；２．演变轴突终未与ＨＲＰ标记胞体形成的轴一体突触；３．溃变轴突终末与非标记树突形成的轴一树突触，４．轴－轴－树连续性突触；５．非溃变的含扁平小泡或多形小泡轴突终末与ＨＲＰ标记的神经元胞体形成的轴一体突触。本文首次报道了猫后根初级传入终未与后东核丘脑投射神经元间的直接突触联系形式为轴－树和轴－体突触，同时也报道了以树突为中心的突触复合体。本研究结果为阐明后索核内非伤害性信息传递与整合的作用方式提供了直接的形态学资料。

In order to identify the synaptic relationship between the primary afferent terminals and the thalamic projecting neurons in the dorsal column nucleus,the combined retrograde transport of horseradish peroxidase(HRP)and experimental degeneration method were applied in the adult cats.50% HRP was injected contralaterally(0.25 μl)into the ventroposterolateral thalamic nucleus after section of C4-T1 L4-S1 dorsal roots on the side ipsilateral to the dorsal column nucleus(DCN).Five types of synapses were observed in the DCN:(1)degenerating axonal terminals formed axo-dendritic synapses with HRP labelled dendrites;(2)degenerating axonal terminals formed axo-somatic synapses with HRP labelled neurons;(3)degenerating axonal terminals were pre-synaptic to non-HRP labelled dendreites,and were themselves postsynaptic to axon terminals containing flattened vesicles;(4)degenerating axonal terminals formed axo-dendritic synapses with non-HRP labelled dendrites;(5) axonal terminals containing flattened or pleomorphic vesicles formed axo-somatic synapses with HRP labelled neurons.The results of the present study demonstrated that the degenerating primary afferent terminals in DCN formed direct monosynaptic contact with the thalamic projecting neurons by axodendritic and axo-somatic synapses.Additionally,convergent synaptic complexes with a dendrite as the central component were also found in DCN.