Anders J J, Hurlock J A
Department of Anatomy and Cell Biology, F. Edward Hebert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814, USA.
Exp Neurol. 1996 Nov;142(1):144-50. doi: 10.1006/exnr.1996.0185.
The olfactory system is the only region of the mammalian central nervous system in which degeneration of the primary sensory neurons results in the development of new neurons and reinnervation of the secondary sensory neurons. Axotomy of the olfactory nerve at the cribriform plate does not cause the formation of a glial scar which blocks nerve regeneration. The purpose of this study was to determine whether a glial scar that formed in the optic nerve would suppress axonal regeneration when transplanted to the site of olfactory nerve axotomy. Primary olfactory neurons were axotomized along the cribriform plate in adult rats. A compact glial scar formed by transection of an adult rat optic nerve 50 to 60 days prior to removal was transplanted into the olfactory nerve axotomy site. The rats were allowed to survive for 1, 2, 3, or 4 weeks. Transport of horseradish peroxidase (HRP) from the nasal cavity by the olfactory neurons was used to examine the temporal and spatial pattern of regeneration of the olfactory nerve after axotomy and axotomy followed by glial scar transplantation. Twenty-one days after olfactory nerve axotomy, HRP was found in the glomerular layer where the primary olfactory axons synapse on the apical dendrites of the secondary olfactory neurons. In the presence of the transplanted glial scar, HRP labeling was not found in certain glomeruli even at 4 weeks postaxotomy. Glial scars formed within the optic nerve impede reinnervation of the olfactory bulb by neurons which have an exceptional regenerative capacity due in part to the ensheathing glia.
嗅觉系统是哺乳动物中枢神经系统中唯一的一个区域，在该区域中，初级感觉神经元的退化会导致新神经元的发育以及次级感觉神经元的重新支配。在筛板处切断嗅神经不会导致形成阻碍神经再生的胶质瘢痕。本研究的目的是确定当将在视神经中形成的胶质瘢痕移植到嗅神经切断部位时，是否会抑制轴突再生。在成年大鼠中，沿着筛板切断初级嗅觉神经元的轴突。将在移除前50至60天切断成年大鼠视神经所形成的致密胶质瘢痕移植到嗅神经切断部位。让大鼠存活1、2、3或4周。利用嗅觉神经元从鼻腔运输辣根过氧化物酶（HRP）来检查嗅神经切断后以及嗅神经切断后进行胶质瘢痕移植时嗅神经再生的时间和空间模式。嗅神经切断21天后，在初级嗅觉轴突与次级嗅觉神经元的顶端树突形成突触的嗅小球层中发现了HRP。在存在移植的胶质瘢痕的情况下，即使在切断轴突后4周，在某些嗅小球中也未发现HRP标记。在视神经内形成的胶质瘢痕会阻碍具有特殊再生能力（部分归因于成鞘胶质细胞）的神经元对嗅球的重新支配。
