Brain Research Institute, University of Zurich, 8057 Zurich, Switzerland, and Department Health Sciences and Technology, ETH Zürich, 8057 Zurich, Switzerland.
J Neurosci. 2014 Feb 26;34(9):3378-89. doi: 10.1523/JNEUROSCI.4384-13.2014.
After a stroke to the motor cortex, sprouting of spared contralateral corticospinal fibers into the affected hemicord is one mechanism thought to mediate functional recovery. Little is known, however, about the role of the phylogenetically old, functionally very important brainstem-spinal systems. Adult mice were subjected to a unilateral photothrombotic stroke of the right motor cortex ablating 90% of the cross-projecting corticospinal cells. Unilateral retrograde tracing from the left cervical spinal hemicord devoid of its corticospinal input revealed widespread plastic responses in different brainstem nuclei 4 weeks after stroke. Whereas some nuclei showed no change or a decrease of their spinal projections, several parts of the medullary reticular formation as well as the spinally projecting raphe nuclei increased their projections to the cortically denervated cervical hemicord by 1.2- to 1.6-fold. The terminal density of corticobulbar fibers from the intact, contralesional cortex, which itself formed a fivefold expanded connection to the ipsilateral spinal cord, increased up to 1.6-fold specifically in these plastic, caudal medullary nuclei. A second stroke, ablating the originally spared motor cortex, resulted in the reappearance of the deficits that had partially recovered after the initial right-sided stroke, suggesting dependence of recovered function on the spared cortical hemisphere and its direct corticospinal and indirect corticobulbospinal connections.
大脑运动皮层中风后，对侧皮质脊髓束纤维向患侧半脊髓的发芽是介导功能恢复的一种机制。然而，关于在系统发生上古老但功能非常重要的脑干-脊髓系统的作用，我们知之甚少。成年小鼠的右侧运动皮层发生光血栓性中风，使 90%的交叉投射皮质脊髓细胞消融。中风后 4 周，从没有皮质脊髓传入的左侧颈脊髓半脊髓进行单侧逆行追踪，揭示了不同脑干核中的广泛可塑性反应。虽然一些核没有变化或其脊髓投射减少，但延髓网状结构的几个部分以及投射到脊髓的中缝核增加了其对皮质去神经支配的颈脊髓半脊髓的投射，增加了 1.2-1.6 倍。来自完整对侧皮质的皮质延髓纤维的终末密度本身形成了对同侧脊髓的五倍扩展连接，在这些可塑性的尾侧延髓核中增加了 1.6 倍。第二次中风消融了最初保留的运动皮层，导致部分恢复后的初始右侧中风后再次出现缺陷，这表明恢复的功能依赖于保留的皮质半球及其直接皮质脊髓和间接皮质延髓脊髓连接。
