Cortical target depletion and the developing lateral geniculate nucleus: implications for trophic dependence.
Cortical target depletion and the developing lateral geniculate nucleus: implications for trophic dependence.
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皮质目标耗竭和发育中的外侧膝状核：对营养依赖性的影响。
DOI：
10.1093/cercor/6.3.446
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
Finlay,BL
中科院分区：
文献类型：
--
作者：
Woo,TU;Niederer,JK;Finlay,BL
发育中的膝状背外侧核（LGd）依赖于视觉皮层的生存已经得到了很好的证明。在出生后早期发育过程中完全切除视觉皮层会导致LGd变性。为了进一步探索这种营养关系的本质，我们通过向怀孕的仓鼠腹腔注射不同剂量的有丝分裂抑制剂MAM（甲基氧化甲醇醋酸酯），在这些神经元在心室区生成时，减少了遗传皮质轴突、第四层神经元和核上神经元的可变比例的主要目标。我们证明，在IV层损失超过75%后，LGd中的细胞数量没有减少。将HRP（辣根过氧化物酶）注射到成年动物的LGd中显示出基本正常的终止模式，没有证据表明遗传皮质轴突向其他皮质区域转移，也没有代偿性地增加第六层和第六层（亚板）的树突。髓皮质轴突主要终止于V层以上的衰竭皮层中层，树杈的范围和密度明显降低。高剂量的MAM处理导致II-IV层细胞损失更严重，IV层细胞明显丢失，基因皮质乔木化的程度和密度进一步降低。可以检测到膝状神经元的大小和总数的减少。在IV层神经元消耗75%以上时，存活的LGd神经元数量与皮层中剩余的II-IV层神经元总数呈线性相关。这些发现是根据可能的营养机制，在发育过程中匹配细胞群的数量进行讨论。
The dependence of the developing dorsal lateral geniculate nucleus (LGd) on visual cortex for survival has been well documented. Complete removal of visual cortex during early postnatal development results in degeneration of the LGd. To further explore the nature of this trophic relationship, we depleted variable proportions of the principal targets of geniculocortical axons, layer IV neurons, and also variable proportions of the supragranular neurons by intraperitoneal injections of different dosages of a mitotic inhibitor MAM (methylazoxymethanol acetate) into pregnant hamsters at the time when these neurons were being generated in the ventricular zone. We demonstrate that after more than 75% loss of layer IV there is no reduction in cell number in the LGd. HRP (horseradish peroxidase) injections into the LGd in adult animals reveal an essentially normal pattern of termination without evidence of rerouting of geniculocortical axons to other cortical areas, nor compensatory increase in arborization in layer VI and VIb (subplate). Geniculocortical axons terminate principally in the middle stratum of the depleted cortex above layer V, with obvious reduction in both the extent and density of arborization. After higher dosages of MAM treatment resulting in more severe cell loss in layers II–IV with the apparent loss of layer IV, the extent and density of geniculocortical arborization are further reduced. Reduction in size as well as total number of geniculate neurons become detectable. Above depletions of 75% of layer IV neurons, the number of surviving LGd neurons is linearly related to the total number of remaining layer II–IV neurons in the cortex. These findings are discussed in light of the possible trophic mechanisms that match cell populations in number during development.