Two modes of corticospinal reinnervation occur close to spinal targets following unilateral lesion of the motor cortex in neonatal hamsters
Two modes of corticospinal reinnervation occur close to spinal targets following unilateral lesion of the motor cortex in neonatal hamsters
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DOI：
10.1016/s0306-4522(98)00424-2
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发表时间：
1999-01-01
期刊：
影响因子：
3.3
通讯作者：
Shimada, M
中科院分区：
文献类型：
--
作者：
Aisaka, A;Aimi, Y;Shimada, M
虽然它已被证明，单侧新生儿皮层消融诱导双侧皮质脊髓的预测，负责这一双边神经支配的途径的解释仍然存在争议。我们假设，这种神经再支配可能是由新形成的纤维发芽的水平喙，或在，或尾锥体交叉。为了验证我们的假设，我们检查了年轻仓鼠的大脑和脊髓，在出生后6天单侧消融右侧运动皮层，然后在出生后21天接受顺行神经元凝集素示踪剂Phaseolus vulgaris-leucoagglutinin注射到左侧运动皮层的后肢区域。为了鉴定腰髓中的运动神经元，其中一些动物还接受了霍乱毒素亚单位B（一种逆行示踪剂）注射到腓肠肌中。定量分析表明，在左侧灰质的腰脊髓凝集素标记是2至8倍，在皮质消融的动物比在完整的动物。免疫组化检测显示，神经支配的左脊髓发生在靠近目标在较低水平的脊髓。两种模式的神经再支配（I型和II型）的完整的皮质脊髓束被确认。I型纤维由从其靶点附近的完整背索发出的再交叉轴突侧支组成，而II型纤维由进入其靶点吻侧几个水平的完整右侧灰质的再交叉母轴突组成，然后改变方向朝向靶点。在较低的脊髓水平的再交叉产生了大量的同侧标记的轴突和它们的终端在灰质的失神经支配的腰髓，具有类似的分布模式上所看到的完整的一面，目前的结果表明，这种同侧的神经支配可能发挥重要作用，在保存和功能的恢复新生儿半皮质损伤。(C)1999年IBRO。出版社：Elsevier Science Ltd
Although it has been shown that unilateral neonatal cortical ablation induces bilateral corticospinal projections, the explanation for the pathways responsible for this bilateral innervation remains controversial. We hypothesized that such reinnervation may be supplied from newly formed fibers sprouting at the level rostral to, or at, or caudal to the pyramidal decussation. In order to test our hypothesis, we examined the brain and spinal cord of young hamsters which had a unilateral ablation of the right motor cortex at six days postnatally, and then received an injection of an anterograde neuronal lectin tracer, Phaseolus vulgaris-leucoagglutinin, into the hindlimb area of the left motor cortex at 21 days postnatally. For the identification of motoneurons in the lumbar spinal cord, some of these animals also received an injection of cholera toxin subunit B, a retrograde tracer, into the gastrocnemius muscle. A quantitative analysis in the left gray matter of the lumbar spinal cord indicated that the lectin labeling was two to eight times higher in cortically ablated animals than in intact animals. Immunohistochemical detection of the lectin revealed that innervation of the left spinal cord occurred close to targets at lower levels in the spinal cord. Two modes of reinnervation (types I and II) by the intact corticospinal tract were recognized. The type I fibers consisted of recrossing axon collaterals sprouted from the intact dorsal funiculus near their targets, while the type II fibers were recrossing parent axons which entered the intact, right gray matter several levels rostral to their targets, and then changed direction toward the targets. The recrossing at lower spinal levels yielded a large number of ipsilaterally labeled axons and their terminals in the gray matter of the denervated lumbar cord, with a distribution pattern similar to that seen on the intact side.The present results indicate that such ipsilateral innervation may play an important role in the sparing and recovery of function following neonatal hemicortical injury. (C) 1999 IBRO. Published by Elsevier Science Ltd.