Spinal Cord Group, Institute of Neuroscience and Psychology, College of Medicine, Veterinary Medicine and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK.
Neuroscience. 2013 Jun 14;240:83-97. doi: 10.1016/j.neuroscience.2013.02.039. Epub 2013 Feb 27.
Precise mechanisms are required to coordinate the locomotor activity of fore- and hind-limbs in quadrupeds and similar mechanisms persist to coordinate movement of arms and legs in humans. Propriospinal neurons (PSNs) are major components of the networks that coordinate these mechanisms. The b subunit of cholera toxin (CTb) was injected unilaterally into either L1 or L3 segments in order to label ascending and descending propriospinal pathways. Labelled cells were examined with light or confocal microscopy. Cells projecting to lumbar segments were evenly distributed, bilaterally throughout all cervical segments. However many more cells were labelled from L1 injections than L3 injections. Roughly 15% of cells in both sides of the C2 segment was found to be immunoreactive for calretinin and a small number (4%) was immunoreactive for calbindin. Axons projecting from L1 to cervical segments formed predominant ipsilateral projections to the cervical intermediate grey matter and ventral horn. Very large numbers of terminals were concentrated within the ventrolateral motor (VLM) nuclei of C7-8 segments but there was sparse innervation of the contralateral nucleus. The vast majority (85%) of these axon terminals in the ipsilateral VML was immunoreactive for the vesicular glutamate transporter 2 (VGLUT2) and the remaining 15% was immunoreactive for the vesicular GABA transporter (VGAT); many of these contained GABA and/or glycine. Inhibitory and excitatory terminals were also found in the contralateral VLM. Most of the terminals in the VLM made contacts with motoneurons. The major finding of this study is the existence of a substantial excitatory propriospinal pathway that projects specifically to the VLM. Motoneurons in the VLM supply muscles of the axilla therefore this pathway is likely to have a profound influence on the activity of the shoulder joint. This pathway may synchronise lumbar and cervical pattern generators and hence the coordination of locomotor activity in the fore- and hind limbs.
精确的机制需要协调四足动物前后肢的运动活动，类似的机制在人类中仍然存在以协调手臂和腿部的运动。脊髓固有神经元（PSN）是协调这些机制的网络的主要组成部分。霍乱毒素（CTB）的 b 亚基被单侧注入 L1 或 L3 段，以标记上行和下行固有脊髓通路。使用光镜或共聚焦显微镜检查标记的细胞。投射到腰椎段的细胞均匀分布，双侧分布在所有颈段。然而，从 L1 注射中标记的细胞比从 L3 注射中标记的细胞多得多。在 C2 段的两侧，大约有 15%的细胞对 calretinin 免疫反应，一小部分（4%）对 calbindin 免疫反应。从 L1 投射到颈段的轴突形成了主要的同侧投射到颈中间灰质和腹角。大量的末端集中在 C7-8 段的腹外侧运动核（VLM）内，但对侧核的神经支配稀疏。这些同侧 VML 中的绝大多数（85%）轴突末端对囊泡谷氨酸转运体 2（VGLUT2）免疫反应，其余 15%对囊泡 GABA 转运体（VGAT）免疫反应；其中许多含有 GABA 和/或甘氨酸。在对侧 VLM 中也发现了抑制性和兴奋性末端。VLM 中的大多数末端与运动神经元接触。这项研究的主要发现是存在一条特定投射到 VLM 的大量兴奋性固有脊髓通路。VLM 中的运动神经元供应腋窝的肌肉，因此这条通路可能对肩关节的活动有深远的影响。这条通路可能会同步腰椎和颈椎模式发生器，从而协调前后肢的运动活动。
