Same spinal interneurons mediate reflex actions of group Ib and group II afferents and crossed reticulospinal actions
Same spinal interneurons mediate reflex actions of group Ib and group II afferents and crossed reticulospinal actions
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DOI：
10.1152/jn.01262.2005
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发表时间：
2006-06-01
影响因子：
2.5
通讯作者：
Jankowska, E.
中科院分区：
文献类型：
--
作者：
Cabaj, A.;Stecina, K.;Jankowska, E.
本研究的目的是分析神经元网络介导中枢发起的运动和反射反应引起的外周传入神经元之间的相互作用，特别是是否interneurons从组Ib传入和组II肌肉传入的通路介导的行动，脊髓运动神经元的网状脊髓神经元位于对侧连合interneurons。为此，在氯醛糖麻醉猫的对侧内侧纵束（MLF）中刺激网状脊髓束纤维，其中同侧脊髓的一半在腰骶部扩大处被横断。在大多数介导Ib组和II组传入神经反射动作的中间神经元中，MLF刺激诱发兴奋性或抑制性突触后电位（EPSP和IPSP，分别）或EPSP和IPSP两者归因于连合中间神经元的双突触动作。此外，在某些中间神经元中，与MLF纤维的交叉轴突侧支的单突触作用相一致的突触诱发电位在潜伏期被诱发。从运动神经元的细胞内记录表明，从Ib组和II组传入的兴奋和抑制调制的对侧下行网状脊髓神经元。结果导致的结论是，连合中间神经元激活的网状脊髓神经元不仅直接影响运动神经元，但也通过增强或减弱激活的前运动中间神经元的途径，从Ib组和II组传入。结果还表明，兴奋性和抑制性运动前中间神经元的影响，以这种方式和连合中间神经元可能有助于在选择的反射动作的Ib组和II组传入在中枢发起的运动。
The aim of the study was to analyze interactions between neuronal networks mediating centrally initiated movements and reflex reactions evoked by peripheral afferents; specifically whether interneurons in pathways from group Ib afferents and from group II muscle afferents mediate actions of reticulospinal neurons on spinal motoneurons by contralaterally located commissural interneurons. To this end reticulospinal tract fibers were stimulated in the contralateral medial longitudinal fascicle (MLF) in chloralose-anesthetized cats in which the ipsilateral half of the spinal cord was transected rostral to the lumbosacral enlargement. In the majority of interneurons mediating reflex actions of group Ib and group II afferents, MLF stimuli evoked either excitatory or inhibitory postsynaptic potentials (EPSPs and IPSPs, respectively) or both EPSPs and IPSPs attributable to disynaptic actions by commissural interneurons. In addition, in some interneurons EPSPs were evoked at latencies compatible with monosynaptic actions of crossed axon collaterals of MLF fibers. Intracellular records from motoneurons demonstrated that both excitation and inhibition from group Ib and group II afferents are modulated by contralaterally descending reticulospinal neurons. The results lead to the conclusion that commissural interneurons activated by reticulospinal neurons affect motoneurons not only directly, but also by enhancing or weakening activation of premotor interneurons in pathways from group Ib and group II afferents. The results also show that both excitatory and inhibitory premotor interneurons are affected in this way and that commissural interneurons may assist in the selection of reflex actions of group Ib and group II afferents during centrally initiated movements.