Ipsilateral actions of feline corticospinal tract neurons on limb motoneurons
Ipsilateral actions of feline corticospinal tract neurons on limb motoneurons
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DOI：
10.1523/jneurosci.1941-04.2004
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发表时间：
2004-09-08
影响因子：
5.3
通讯作者：
Hammar, I
中科院分区：
文献类型：
--
作者：
Edgley, SA;Jankowska, E;Hammar, I
产生于初级运动皮层的外侧锥体束（PT）神经元是控制意志性肢体运动的主要途径。然而，对侧轻偏瘫后PT神经元损伤的一侧可能会抵消同侧的PT神经元的行动，从未受损的一面。为了探讨脊髓继电器通过PT神经元可能会影响同侧运动神经元，我们分析了诱发的突触动作后，切断对侧PT的下行纤维在低胸水平的同侧锥体后肢运动神经元的刺激。结果表明，同侧PT神经元可以通过激活对侧下行网状脊髓神经元，从而激活脊髓连合中间神经元，这些中间神经元向后投射到受刺激的锥体束同侧的运动神经元，从而三突触地影响肢体运动神经元。单独刺激锥体并不能引起运动神经元的突触活动，但能有效地促进内侧纵束网状脊髓束纤维刺激引起的突触后复极和突触后复极。与此双交叉通路平行，皮质脊髓神经元也可以通过同侧下行网状脊髓束纤维引起同侧动作，通过同侧位于脊髓中间神经元起作用。由于连合中间神经元介导的活动强于同侧前运动中间神经元，因此本研究得出结论，皮质脊髓神经元通过连合中间神经元的同侧活动可能为皮质脊髓束损伤所致轻偏瘫的功能恢复提供更好的机会。
Contralateral pyramidal tract ( PT) neurons arising in the primary motor cortex are the major route through which volitional limb movements are controlled. However, the contralateral hemiparesis that follows PT neuron injury on one side may be counteracted by ipsilateral of actions of PT neurons from the undamaged side. To investigate the spinal relays through which PT neurons may influence ipsilateral motoneurons, we analyzed the synaptic actions evoked by stimulation of the ipsilateral pyramid on hindlimb motoneurons after transecting the descending fibers of the contralateral PT at a low thoracic level. The results show that ipsilateral PT neurons can affect limb motoneurons trisynaptically by activating contralaterally descending reticulospinal neurons, which in turn activate spinal commissural interneurons that project back across to motoneurons ipsilateral to the stimulated pyramidal tract. Stimulation of the pyramids alone did not evoke synaptic actions in motoneurons but potently facilitated disynaptic EPSPs and IPSPs evoked by stimulation of reticulospinal tract fibers in the medial longitudinal fascicle. In parallel with this double-crossed pathway, corticospinal neurons could also evoke ipsilateral actions via ipsilateral descending reticulospinal tract fibers, acting through ipsilaterally located spinal interneurons. Because the actions mediated by commissural interneurons were found to be stronger than those of ipsilateral premotor interneurons, the study leads to the conclusion that ipsilateral actions of corticospinal neurons via commissural interneurons may provide a better opportunity for recovery of function in hemiparesis produced by corticospinal tract injury.