Key Laboratory of Nanopharmacology and Nanotoxicology, Beijing Institute of Pharmacology and Toxicology, 27 Taiping Road, Beijing, 100850, China.
Neurosciences Research Institute, Peking University, Key Laboratory of Neuroscience; Department of Neurobiology, Peking University Health Science Center, 38 Xue Yuan Road, Beijing, 100083, China.
Mol Neurobiol. 2016 Dec;53(10):7137-7157. doi: 10.1007/s12035-015-9588-1. Epub 2015 Dec 17.
The nanoscale three-dimensional structures of neurosynapses are unknown, and the neuroanatomical basis of epilepsy remains to be elucidated. Here, we studied the nanoscale three-dimensional synapses between hippocampal neurons, and membranous conjunctions between neurons were found with atomic force microscopy (AFM) and confirmed by transmission electron microscope (TEM), and their pathophysiological significance was primarily investigated. The neurons and dendrites were marked by MAP-2, axons by neurofilament 200, and synapses by synapsin I immunological staining. In the synapsin I-positive neurite ends of the neurons positively stained with MAP-2 and neurofilament 200, neurosynapses with various nanoscale morphology and structure could be found by AFM. The neurosynapses had typical three-dimensional structures of synaptic triplet including the presynaptic neurite end, synaptic cleft of 30 ∼ 40 in chemical synapses and 2 ∼ 6 nm in electrical ones, the postsynaptic neurite or dendrite spine, the typical neurite end button, the distinct pre- and postsynaptic membranes, and the obvious thickening of the postsynaptic membranes or neurites. Some membranous connections including membrane-like junctions (MLJ) and fiber-tube links (FTL) without triplet structures and cleft were found between neurons. The development frequencies of the two membranous conjunctions increased while those of the synaptic conjunctions decreased between the neurons from Otx1 knock-out mice in comparison with those between the neurons from normal mice. These results suggested that the neuroanatomical basis of Otx1 knock-out epilepsy is the combination of the decreased synaptic conjunctions and the increased membranous conjunctions.
神经突触的纳米三维结构尚不清楚，癫痫的神经解剖学基础仍有待阐明。在这里，我们研究了海马神经元之间纳米级三维突触，并用原子力显微镜（AFM）发现并通过透射电子显微镜（TEM）证实了神经元之间的膜性连接，并初步研究了其病理生理学意义。神经元和树突用 MAP-2 标记，轴突用神经丝 200 标记，突触用突触素 I 免疫染色标记。在 MAP-2 和神经丝 200 阳性染色的神经元的突触素 I 阳性神经突末端，可以用 AFM 发现具有各种纳米级形态和结构的神经突触。神经突触具有典型的突触三联体三维结构，包括突触前神经突末端、化学突触的 30∼40nm 宽和电突触的 2∼6nm 宽的突触间隙、突触后神经突或树突棘突、典型的神经突末端按钮、明显的突触前和突触后膜以及突触后膜或神经突的明显增厚。在神经元之间发现了一些膜性连接，包括无三联体结构和间隙的膜状连接（MLJ）和纤维管连接（FTL）。与正常小鼠神经元之间的连接相比，在 Otx1 敲除小鼠的神经元之间，这两种膜性连接的发育频率增加，而突触连接的发育频率降低。这些结果表明，Otx1 敲除癫痫的神经解剖学基础是突触连接减少和膜性连接增加的结合。
