Nacimiento W, Mautes A, Töpper R, Oestreicher A B, Gispen W H, Nacimiento A C, Noth J, Kreutzberg G W
Department of Neurology, Aachen University Medical School, Germany.
J Neurosci Res. 1993 Aug 15;35(6):603-17. doi: 10.1002/jnr.490350604.
Sprouting of dorsal root axons has been suggested to occur in the mature cat spinal cord caudal to a hemisection at a low thoracic level sparing the dorsal columns. The lesion interrupts supraspinal descending projections, while leaving ascending collaterals of dorsal root axons intact. This hypothesis was re-evaluated by comparing the light and electron microscopic immunoreactivity of B-50 (GAP-43) on both sides of the postulated target regions for sprouting, the intermediate gray and the dorsal horn. The neural-specific phosphoprotein B-50 is involved in regenerative and developmental axonal outgrowth and synaptic plasticity. The light microscopic distribution pattern and density of B-50 immunostaining, measured by quantitative densitometry, were bilaterally symmetrical in all segments below the hemisection 3.5, 8, 14, 21, and 56 days postoperatively, as they were in the intact animal. Ultrastructurally, growth cone-like profiles were not detectable during putative periods of sprouting in regions of interest. After removal of degenerated axon terminals, vacated postsynaptic places appeared to be covered by astrocytic processes. These results indicate that, under the present experimental conditions, sprouting of primary afferents in adult cats is unlikely to be involved in functional plasticity after removal of descending pathways.
有研究表明，在成熟猫的脊髓中，胸段下部半横断且保留背柱的情况下，背根轴突会在损伤部位尾侧发生芽生。该损伤中断了脊髓上的下行投射，而背根轴突的上行侧支保持完整。通过比较芽生假定靶区域（中间灰质和背角）两侧B-50（GAP-43）的光镜和电镜免疫反应性，对这一假说进行了重新评估。神经特异性磷蛋白B-50参与轴突再生和发育性生长以及突触可塑性。通过定量密度测定法测量，术后3.5、8、14、21和56天，在半横断以下所有节段，B-50免疫染色的光镜分布模式和密度在两侧是对称的，与完整动物的情况相同。在超微结构上，在假定的芽生期内，未在感兴趣区域检测到生长锥样结构。在去除退化的轴突终末后，空出的突触后位置似乎被星形胶质细胞突起覆盖。这些结果表明，在当前实验条件下，成年猫初级传入纤维的芽生不太可能参与下行通路切断后的功能可塑性。
