猫丘脑腹后外侧核内皮质—丘脑纤维终末与丘脑—皮质投射神经元之间的突触连接

用ＣＢ－ＨＲＰ逆行追踪与顺行溃变相结合的方法，对描丘脑腹后外侧核内的来自大脑皮质体感Ⅰ区的皮质—丘脑纤维终末与丘脑—皮质投射神经元之间的突触连接进行了电镜观察。向猫大脑皮质体感Ⅰ区内注射ＣＢ－ＨＲＰ５ｈ后，电解损毁原注射部位，术后动物存活４ｄ。电镜下发现丘脑瓜后外侧核内存在５种突触连接方式；（１）溃变的轴突终未与ＨＲＰ标记神经元胞体形成轴－体突触；（２）溃变的轴突终末与ＨＲＰ标记的树突形成轴—树突触；（３）溃变的轴突终末和其它突触前成分共同与中央树突形成汇聚型的突触复合体；（４）溃变的轴突终末与未标记树突形成的轴—树突触；（５）正常的轴突终末与ＨＲＰ标记神经元形成对称型的轴—体突触。

THE SYNAPTIC RELATIONSHIP BETWEEN CORTICOTHALAMIC FIBER TERMINALS AND THALAMOCORTICAL PROJECTION NEURONS IN THE THALAMIC VPL OF CAT

In the present paper the synaptic relationship between corticothalamic fiber terminals from sensory area Ⅰ(SI) and thaIamocortical projection neurons in the ventroposterolateral thalamic nucleus (VPL) of cat was studied by using anterograde degeneration combined with HRP retrograde tracing methods. After CB-HRP injection into the SI area five hours followed by electrolytic lesion in the SI area, animals were surved for four days. Five types of synapses were observed in the ventroposterolateral thalamic nucleus: (1)degenerated axonal terminals made axo-somatic synapses with the cell body of HRP labelled neurons;(2)degenerated axonal terminals made axo-dendriticsynapses with HRP labelled dendrites; (3)degenerated axonal terminals and other presynaptic elements together constituted convergent synaptic complex with the unlabelled dendrites; (4)degenerated axonal terminals made axo-dendritic synapses with unlabelled dendrites; (5)normal axonal terminals made axo-somatic synapses with the cell body of HRP labelled neurons. The results of the present study demonstrated that corticothalamic fibers terminals in VPL made direct monosynaptic connection with the thalamocortic relay neurons by axodendritic and axo-somatic synapses. The direct synaptic relationship between corticothalamic fiber terminals and thalamocortical projection neurons discovered in this study provides synaptic basis for the further study of physiology.