ON THE DEVELOPMENT OF THE PYRAMIDAL TRACT IN THE RAT .2. AN ANTEROGRADE TRACER STUDY OF THE OUTGROWTH OF THE CORTICOSPINAL FIBERS
ON THE DEVELOPMENT OF THE PYRAMIDAL TRACT IN THE RAT .2. AN ANTEROGRADE TRACER STUDY OF THE OUTGROWTH OF THE CORTICOSPINAL FIBERS
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DOI：
10.1007/bf00315460
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发表时间：
1986-01-01
期刊：
影响因子：
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通讯作者：
NIEUWENHUYS, R
中科院分区：
文献类型：
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作者：
GRIBNAU, AAM;DEKORT, EJM;NIEUWENHUYS, R
本文用麦胚凝集素-辣根过氧化物酶（WGA-HRP）对发育中的大鼠皮质脊髓束（CST）进行了顺行示踪研究。正常Rager染色材料的分析显示，皮质脊髓轴突在出生当天（PO）到达上颈脊髓水平。出生后1（P1）至14（P14）天的大鼠接受多次WGA-HRP注射到其左半球的皮质中，并允许存活24 h。第一个标记的CST纤维尾侧延伸到第三胸脊髓节段在P1;到第八胸节段在P3;到第一或第二腰节段在P7和第二至第三骶节段在Pg。因此，CST的领先的“先锋”纤维的生长在P9完成，但后来发展的轴突不断增加，甚至超过P9。定量分析的标签量沿着的长度向外生长的CST揭示了一个特征模式的标签随年龄的变化。该模式最显著的特征是：（1）分别在颈和腰膨大水平形成两个直立峰;（2）暂时存在一个较小的运行峰，该峰随生长束的前部向尾侧移动。站立的峰值归因于在两个膨胀的轴突终端的分支，而运行的峰值可能产生的示踪剂内的生长锥的尖端处的生长的CST轴突的积累。因素，如轴突的数量，不同的轴突直径，分支的侧枝，存在的variocosities，示踪剂的运输速率，在注射部位的示踪剂的摄取，这可能会影响标签的量存在于整个束和在个别轴突进行了讨论。目前的研究集中在分析皮质内注射部位与CST标记模式之间的关系。延迟两天之间的CST轴突在特定的脊髓水平的到来，他们的生长到相邻的脊髓灰质。然而，结合HRP和电子显微镜实验是必要的，以确定背后的因素成熟的CST以及成熟的脊髓灰质。
An anterograde tracer study has been made of the developing corticospinal tract (CST) in the rat using wheat germ agglutinin-conjugated horseradish peroxidase (WGA-HRP). Analysis of normal Rager stained material revealed that corticospinal axons reach upper cervical spinal cord levels at the day of birth (PO). Postnatal rats ranging in age from one (P1) to fourteen (P14) days received multiple WGA-HRP injections into the cortex of their left hemisphere and were allowed to survive for 24 h. The first labeled CST fibers caudally extend into the third thoracic spinal cord segment at P1; into the eight thoracic segment at P3: into the first or second lumbar segment at P7 and into the second to third sacral segment at Pg. Thus the outgrowth of the leading ''pioneer'' fibers of the CST is completed at P9 but later developing axons are continuously added even beyond P9. Quantitative analysis of the amount of label along the length of the outgrowing CST revealed a characteristic pattern of labeling varying with age. The most striking features of that pattern are: (1) the formation of two standing peaks at the level of the cervical and lumbar enlargements respectively and (2) the transient presence of a smaller running peak which moved caudally with the front of the outgrowing bundle. The standing peaks are ascribed to the branching of the axon terminals at both intumescences, whereas the running peak probably arises by the accumulation of tracer within the growth cones at the tips of the outgrowing CST axons. Factors such as the number of axons, the varying axon diameters, the branching collaterals, the presence of variocosities, the transport rate of the tracer, the uptake of the tracer at the injection sites, which possibly may affect the amount of label present in both the entire bundle and in the individual axons are discussed. Current research is focussed upon an analysis of the relation between the site of injection within the cortex and the pattern of labeling of the CST. A delay of two days was found between the arrival of the CST axons at a particular spinal cord level and their outgrowth into the adjacent spinal gray. However, combined HRP and electronmicroscopic experiments are necessary to determine the factors behind the maturation of the CST as well as the maturation of the spinal gray.