Functional differentiation and organization of feline midlumbar commissural interneurones
Functional differentiation and organization of feline midlumbar commissural interneurones
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DOI：
10.1113/jphysiol.2005.083014
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发表时间：
2005-06-01
影响因子：
5.5
通讯作者：
Hammar, I
中科院分区：
文献类型：
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作者：
Jankowska, E;Edgley, SA;Hammar, I
连接脊髓两侧的中间神经元（连合中间神经元）对于肢体间协调至关重要，但人们对其组织知之甚少。我们检查了位于中腰段的连合中间神经元的输入，并投射到对侧运动核，旨在确定它们是否形成不同的亚群。根据 78 个中间神经元的细胞内记录，确定了两个主要的非重叠亚群：一个由 II 组肌肉传入神经元单突触兴奋 (n = 10)，另一个由网状脊髓神经元单突触兴奋 (n = 52)。在具有单突触网状脊髓的患者中发现了来自 I 组肌肉传入和/或前庭脊髓束神经元的单突触输入，但在 II 组输入中没有发现，以及在一些其他神经症患者中 (n = 6)。在其余 10 个中间神经元中仅发现来自这些来源的突触输入。来自同侧和对侧肌肉传入以及下降束的双突触兴奋性输入的分布选择性较低，并且可能介导中间神经元与单突触传入或下降输入的共兴奋。然而，主要的双突触和多突触输入是抑制性的。 IPSP 是由高比例的由 II 组传入神经单突触兴奋的连合中间神经元的下行束诱发的 (55%)，以及由网状脊髓纤维单突触兴奋的高比例的连合中间神经元的 II 组传入神经诱发的 (78%)。这种分布表明，这两个亚群在中枢发起的运动或反射调整中被差异激活，而不是共同激活。这与之前的证明一致，即去甲肾上腺素对两个亚群的连合神经元有不同的影响。
Interneurones interconnecting the two sides of the spinal cord (commissural interneurones) are critically important for interlimb coordination, but little is known about their organization. We have examined the inputs to commissural interneurones located in the midlumbar segments with projections to contralateral motor nuclei, aiming to determine whether they form distinct subpopulations. Based on intracellular records from 78 interneurones, two major non-overlapping subpopulations were identified: one monosynaptically excited by group II muscle afferents (n = 10), the other monosynaptically excited by reticulospinal neurones (n = 52). Monosynaptic input from group I muscle afferents and/or from vestibulospinal tract neurones was found in those with monosynaptic reticulospinal, but not group II input, and in a few other neurotics (n = 6). Only disynaptic input from these sources was found in the remaining 10 interneurones. Disynaptic excitatory input from ipsilateral and contralateral muscle afferents and from descending tracts was distributed less selectively and might mediate coexcitation of interneurones with monosynaptic afferent or descending input. The dominant disynaptic and polysynaptic input was, however, inhibitory. IPSPs were evoked from the descending tracts in a high proportion of the commissural interneurones that were monosynaptically excited by group II afferents (55%) and from group II afferents in a high proportion of the commissural interneurones that were monosynaptically excited by reticulospinal fibres (78%). This distribution suggests that the two subpopulations are activated differentially, rather than being coactivated, in either centrally initiated movements or reflex adjustments. This would be consistent with the previous demonstration that noradrenaline differentially affects commissural neurones of the two subpopulations.