Naegele J R, Jhaveri S, Schneider G E
Department of Brain Sciences, Massachusetts Institute of Technology, Cambridge 02139.
J Comp Neurol. 1988 Nov 22;277(4):593-607. doi: 10.1002/cne.902770411.
During specification of orderly neural maps, axons correctly navigate to their targets and form terminal arbors in topographically correct positions. To learn more about this mapping process, the patterns of geniculocortical topography were correlated with growth of axon arbors in the hamster visual cortex. Topography was studied by retrograde transport of WGA-HRP from area 17 to the dorsal lateral geniculate nucleus (LGd) and visualized with TMB histochemistry. In separate experiments, geniculocortical axon arbors were filled with HRP deposited extracellularly into the optic radiations and stained with cobalt-intensified DAB. On the day of birth (P0) and on P1-2, a crude topography was detected in the geniculocortical system. At these ages, geniculocortical axons coursed in the embryonic white matter of the visual cortex, parallel to the pia. During their passage, multiple short collaterals, with no terminal arbors, were extended into the subplate and deeper portions of the cortical plate. By P3-5, the topography was more precise and simple axonal arbors had now begun to be formed on some branches within the cortical plate. During the second postnatal week, branches in the white matter without terminals were eliminated and the ramifications of branches in the gray matter became more elaborate. The arbors continued to increase in complexity and resembled adult forms by P24.
在有序神经图谱的特化过程中，轴突能正确地导航至其靶标，并在地形学上正确的位置形成终末分支。为了更多地了解这一图谱形成过程，将膝状体皮质的地形学模式与仓鼠视觉皮质中轴突分支的生长情况进行了关联研究。通过将WGA-HRP从17区逆行运输至背外侧膝状核（LGd）来研究地形学，并使用TMB组织化学进行可视化。在单独的实验中，通过将细胞外沉积的HRP注入视辐射中来填充膝状体皮质轴突分支，并用钴增强DAB进行染色。在出生当天（P0）以及P1-2时，在膝状体皮质系统中检测到一种粗略的地形学。在这些年龄段，膝状体皮质轴突在视觉皮质的胚胎白质中走行，与软脑膜平行。在其走行过程中，多个无终末分支的短侧支延伸至皮质下板和皮质板的更深部分。到P3-5时，地形学变得更加精确，并且在皮质板内的一些分支上开始形成简单的轴突分支。在出生后的第二周，白质中无终末的分支被消除，灰质中分支的分支变得更加精细。到P24时，分支继续变得更加复杂，并类似于成年形式。
