中缝背核远位触液神经元与脑实质之间超微结构的联系

ULTRASTRUCTURAL RELATIONSHIP BETWEEN DISTAL NEURONS CONTACTING CEREBROSPINAL FLUID IN DORSAL RAPHE NUCLEUS AND BRAIN PARENCHYMA

目的：研究大鼠中缝背核内远位触液神经元与脑实质结构之间的超微结构联系，以探明这种神经元传递信息的方向。方法：用霍乱毒素亚单位Ｂ与辣根过氧化物酶复合物（ＣＢ－ＨＲＰ）顺、逆行追踪与电镜技术相结合。结果：中缝背核的触液神经元（以“＋”表示）与脑实质的非触液神经元（以“－”表示）之间主要有两种突触形式：轴（－）－树（＋）突触和树（－）－树（＋）突触，标记的树突多成簇状分布，有的形成树突中心球样的结构，在第三脑室侧壁尚见有被标记的轴突终末伸入脑脊液中。这些突触既有 ＧｒａｙⅠ型（兴奋型），也有 Ｇｒａｙ Ⅱ型（抑制型），但它们的共同特点是突触前成分均为非触液神经元的结构构成，突触后成分均为触液神经元的结构构成。结论：中缝背核的远位触液神经元既可以接受兴奋性信息，也可以接受抑制性信息，并将这些信息自脑实质向脑脊液方向传递。

Objective: To study the ultrastructural relationship between distal neurons contacting cere- brospinal fluid (CSF) in the dorsal raphe nucleus (DR) and neurons no-contacting CSF in the brain parenchyma. Methods: An antergrade and retrograde tracing of the cholera toxin subunit B with horseradish peroxidase (CB-HRP) and electron microscope. Results: There were mainly two synaptic types between neurons contacting CSF in DR and neurons no-contacting CSF in the brain parenchyma: A dendro (-)-dendritic (+) synapse and an axo (-)-dendritic (+) synapse ('-' represents neurons no-contacting CSF and '+' represents neurons contacting CSF). The labelled dendrites by CB-HRP distributed in a cluster, and some of them formed dendritic central complex. The labelled axon terminal by CB-HRP extended into CSF in the cavity of the third ventricle. Both type Gray Ⅰ(exciting ) and Gray Ⅱ(inhibiting) synapses were found and the presynaptic elements were formed by neurons no-contacting CSF and the postsynaptic elements by neu- rons contacting CSF. Conclusion: This paper firstly reported that distal neurons contacting CSF in DR could receive both exciting and inhibiting messengers and transmit them from brain parenchyma to CSF.