应用电镜X射线显微分析方法研究神经细胞内钙离子的分布

本文应用X射线能谱分析结合电镜技术研究了钙离子在青蛙交感神经节神经元内的分布及其在茶碱作用下分布的变化.实验结果表明在组织样品的电子致密沉积物EDD中含有钙离子成分.在青蛙交感神经节突触后神经元中,包含钙离子的EDD存在于质膜、亚表面池及线粒体中;在突触前神经末梢中,突触小泡的膜上也可观察到EDD.在茶碱作用下,交感神经节神经元的质膜、线粒体中的EDD大大地减少;在亚表面池中则没有或很少观察到EDD;突触前末梢中的突触小泡明显地趋向聚集,在突触小泡之间的连接处频繁地出现EDD.本文根据实验结果讨论了茶碱可能促使钙离子从交感神经元的上述部位中释放出来,并认为质膜、亚表面池和线粒体是细胞内钙离子的贮存部位,而亚表面池可能是主要的贮存释放部位.突触前神经末梢内形态上的变化可能与神经递质释放的机理有关.

STUDIES ON NEURONAL CALCIUM LOCALIZATION BY USING ELECTRON MICROSCOPY WITH X-RAY MICROPROBE ANALYSIS

The effects of theophylline on Ca2 + localization in sympathetic ganglia of bullfreg were studied by using electron microscopy with X-ray microprobe analysis technique.Electron microscopic examination of the tissue revealed electron-dense deposits (EDD) in the plasma membrane, subsurface cisternae and mitochondria of sympathetic neurons.In presynaptic terminals, deposits were found on the membrane of synaptic vesicles. These EDD were proved to contain calcium by X-ray microprobe analysis. The addition of 10mM/L theophylline greatly reduced the deposits in plasma membrane, mitochondria and EDD were not observed or observed rarely in subsurface cisternae.In presynaptic terminals,synaptic vesicles tended to aggregate after treatment with theophylline and EDD were frequently observed at points where adjacent vesicles were opposed.If the EDD provide an indication of Ca2+ localization,the results suggest that theophylline may release Ca2+ associated with subsurface cisternae, plasma membrane, mitochondria and subsurface cisternae may be a primarily functional Ca2+ storage site in the ganglion cell.These morphological changes in presynaptic terminals will presumably be reflected in alterations in transmitter release.