大鼠下丘脑第三脑室周催产素样神经元与脑脊液关系的电镜研究

CSF CONTACTING OXYTOCIN-IMMUNOREACTIVE NEURONAL STRUCTURES IN THE RAT THIRD VENTRICLE: AN IMMUNOELECTRON MICROSCOPIC STUDY

本研究用高浓度戊二醛灌注固定、包埋前ABC免疫酶染色方法,显示了大鼠下丘脑第三脑室周与脑脊液密切相关的室管膜内及室管膜下OT-LI神经元丛。结果发现:在室旁核后大细胞亚核水平,第三脑室腔的顶及底部常有一些OT-LI轴突终末突入第三脑室腔,与脑脊液相接触,其纤维来源不明;透射电镜下见:这些OT-LI轴突终末附于室管膜细胞之上或夹行于微绒毛之间,常与第三脑室室管膜形成一种类似突触的连接,绝大多数OT-LI轴突终末内含有大量线粒体,其轴突包膜均呈节段性增厚。在视前区至室间孔水平的第三脑室底部,可见到OT-LI神经元胞体突入室管膜细胞间,似部分与脑脊液直接接触,透射电镜下见此类OT-LI神经细胞仅隔一层极薄的室管膜细胞浆与脑脊液相接触。在第三脑室侧壁室管膜下常有较密集的室管膜下神经元树突丛,透射电镜下常见到紧贴室管膜下走行的OT-LI树突,而且往往有轴突与之形成轴-树突触。上述结果提示,室管膜下的OT-LI神经元及树突可能既接受脑脊液中各种信息物质的调控又受到一些传入神经轴突终末的突触性传入控制而实施其分泌活动;突入脑室腔的OT-LI辅突可能是脑脊液中OT的产生途径之一。

The rats were perfused with aldehyde fixatives containing high concentrations of glutaraldehyde. Pre-embedding immunoperoxidase staining method was used to allow visualization of the ultrastructure of CSF contacting oxytocin-like immunoreactive (OT-Li)elements in and around the third ventricle of the hypothalamus in the rat. Supraependymal OT-Li axons were found on the roof and the floor Of the third ventricle at the level of the paraventricular nucleus. These axons formed synapse-like junction with the ependyma, usually they were surrounded by microvilli of the ependymal cells. Most of the supraependymal OT-Li axons were filled with mitochondria and some clear and large dense-corcd vesicles. Intraependymal OT-Li cells were localized between the cpendymal cells on the floor of the preoptic third ventricle, and only a thin sheet of the ependymal cytoplasm could be detected betwecn the OT-Li cells and the CSF. Subependymal OT-Li dendrites were usually observed along the lateral wall and the floor of the third ventricle in the hypothalamus, often receiving asymmetric axodendritic contacts. The close proximity of the OT-Li neurons to the CSF and the processes of OT-Li axons in the 3rd ventricle suggest that the OT-Li neurons may monitor the changes in the CSF and may be one of the sources of OT in the CSF. The presence of synapse on the subependymal OT-Li dendrites suggests that they receive neural inputs as well.