CHICK WING INNERVATION .3. FORMATION OF AXON COLLATERALS IN DEVELOPING PERIPHERAL-NERVES
CHICK WING INNERVATION .3. FORMATION OF AXON COLLATERALS IN DEVELOPING PERIPHERAL-NERVES
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DOI：
10.1002/cne.903570207
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发表时间：
1995-06-26
影响因子：
2.5
通讯作者：
HOLLYDAY, M
中科院分区：
文献类型：
--
作者：
FERNS, MJ;HOLLYDAY, M
脊椎动物肢体神经支配过程中的轴突导航已被证明与轴突生长锥的大小和复杂性的位置相关，有时还与终末生长锥的分叉和轴突分支有关(Hollyday和Morgan-Carr，配对论文)。我们进一步研究了轴突分支，并询问它是否延伸到侧支向不同神经的投射。在第28-35期，将辣根过氧化物酶或DIL注射到鸡胚翅膀的单个周围神经中，并在组织切片中追踪注射部位近端的固体标记轴突的轨迹。在周围神经最初在肩部形成的阶段，经常观察到逆行标记的轴突侧支投射到注射部位近端的未注射神经中。这些两神经侧支是由所研究的高比例胚胎中的一小部分轴突形成的，既可以出现在运动轴突中，也可以出现在感觉轴突中。在沿肢体近端轴线和前后轴线分离的神经之间可以观察到两条神经侧支投射，但在空间上仅限于供应邻近肢体区域的神经，而投射到肢体不同区域的神经之间从未见过两条神经侧支投射。在投射到背侧和腹侧通路的神经丛上看不到侧支。从28-29期到32期，双神经侧支的表观频率逐渐下降；33期及以上时，近侧翼未见二神经侧支。它们的消除机制目前尚不清楚。这些观察表明，在生长过程中看到的一些轴突分支足够分化，导致轴突侧支投射到两个不同的周围神经。据推测，双神经侧支既反映了神经元的分支能力，也反映了轴突引导机制中的一些不精确。这些加在一起会导致投影中的微小误差，这些误差随后会被消除。(C)1995年Wiley-Liss公司
Axon navigation during vertebrate limb innervation has been shown to be associated with position-dependent changes in size and complexity of the axon growth cones, and sometimes with bifurcation of terminal growth cones and axon branching (Hollyday and Morgan-Carr, companion paper). We have further examined axon branching and asked whether it extends to the projection of collaterals to different nerves. Injections of horseradish peroxidase or Dil were made into individual peripheral nerves in the wings of chick embryos at stages 28-35, and the trajectories of solidly labeled axons were traced proximally from the injection site in tissue sections. During stages when the peripheral nerves were first forming in the shoulder region, collaterals of retrogradely labeled axons were frequently observed to project into uninjected nerves proximal to the injection site. These two-nerve collaterals were formed by a small percentage of axons in a high percentage of the embryos studied and could occur in both motor and sensory axons. Two-nerve collateral projections were observed between nerves separated along both the proximodistal and anteroposterior axes of the limb, but they were limited in spatial extent to nerves supplying adjacent limb regions and were never seen between nerves projecting to widely disparate regions of the limb. Collaterals were not seen at the plexus projecting to both dorsal and ventral pathways. The apparent frequency of two-nerve collaterals was found to decline progressively from stage 28-29 to stage 32; no two-nerve collaterals were seen in the proximal wing at stage 33 and older. The mechanism of their elimination is presently unknown. These observations suggest that some axon branching seen during outgrowth is sufficiently divergent to result in axon collaterals which project to two different peripheral nerves. Presumably, two-nerve collaterals reflect both the neuron's ability to branch and some imprecision in the axonal guidance mechanisms. Together these give rise to minor errors in projection which are subsequently removed. (C) 1995 Wiley-Liss, Inc.