Hayashi Kensuke, Kawai-Hirai Rika, Harada Akihiro, Takata Kuniaki
Department of Cell Biology, Institute for Molecular and Cellular Regulation, Gunma University, 3-39-15 Showamachi, Maebashi, Gunma 371-8512, Japan.
J Cell Sci. 2003 Nov 1;116(Pt 21):4419-28. doi: 10.1242/jcs.00762. Epub 2003 Sep 16.
Inhibitory and excitatory neurons exhibit distinct patterns of development in the mammalian cerebral cortex. The morphological development of inhibitory and excitatory neurons derived from fetal rat cerebral cortex has now been compared in vitro. Inhibitory neurons were identified by immunofluorescence staining with antibodies to gamma-aminobutyric acid, and axon formation was detected by staining with antibodies to phosphorylated neurofilaments. In chemically defined, glia-free and low-density cultures, excitatory neurons formed axons within three days of plating. By contrast, inhibitory neurons required more than six days to form axons. Time-lapse analysis over six days revealed that most inhibitory neurons were bipolar and that their two processes exhibited alternate growth and retraction without giving rise to axons. Movement of the cell body towards the growing process was apparent in about one-half of inhibitory neurons, whereas such movement was never seen in excitatory neurons. The migratory behavior of neurons was further investigated by culture on a glial cell monolayer. Inhibitory neurons migrated over substantially larger distances than did excitatory neurons. The centrosome of inhibitory neurons translocated to the base of the newly emerging leading process, suggesting the existence of a force that pulls intracellular organelles towards the leading process. Centrosome translocation was not detected in excitatory neurons. These observations suggest that the developmental programs of excitatory and inhibitory neurons differ. Inhibitory neurons thus possess a more effective cytoskeletal machinery for migration than excitatory neurons and they form axons later.
抑制性神经元和兴奋性神经元在哺乳动物大脑皮层中呈现出不同的发育模式。目前已在体外比较了源自胎鼠大脑皮层的抑制性神经元和兴奋性神经元的形态发育。通过用抗γ-氨基丁酸抗体进行免疫荧光染色来鉴定抑制性神经元，并用抗磷酸化神经丝抗体染色来检测轴突形成。在化学成分明确、无胶质细胞且低密度的培养条件下，兴奋性神经元在接种后的三天内形成轴突。相比之下，抑制性神经元需要超过六天才能形成轴突。为期六天的延时分析显示，大多数抑制性神经元是双极的，其两个突起呈现交替生长和回缩，不会形成轴突。在大约一半的抑制性神经元中，细胞体向生长突起的移动很明显，而在兴奋性神经元中从未见过这种移动。通过在胶质细胞单层上培养进一步研究了神经元的迁移行为。抑制性神经元的迁移距离比兴奋性神经元长得多。抑制性神经元的中心体转移到新出现的领先突起的基部，这表明存在一种将细胞内细胞器拉向领先突起的力。在兴奋性神经元中未检测到中心体转移。这些观察结果表明，兴奋性神经元和抑制性神经元的发育程序不同。因此，抑制性神经元比兴奋性神经元拥有更有效的迁移细胞骨架机制，并且它们形成轴突的时间更晚。
