Wenner P, Frank E
Neurobiology Department, University of Pittsburgh, School of Medicine, Pennsylvania 15261, USA.
J Neurosci. 1995 Dec;15(12):8191-8. doi: 10.1523/JNEUROSCI.15-12-08191.1995.
The source of environmental cues determining the central connections of muscle sensory neurons was investigated by manipulating chick embryos so that sensory neurons supplied a duplicate set of dorsal thigh muscles. These neurons projected out ventral nerve pathways and along motor axons that normally project to ventral muscles but their ultimate target tissue was the duplicate set of dorsal muscles. The central connections of these sensory neurons to motoneurons supplying normal dorsal muscles were then determined with intracellular recordings in isolated spinal cord preparations. Sensory neurons supplying individual duplicate dorsal muscles made the same connections as those supplying the corresponding normal dorsal muscles; the pattern of these connections was different than that made by afferents supplying ventral muscles. Sensory neurons thus made synaptic connections appropriate for their target muscle rather than for their more proximal ventral environment. These findings suggest that the target muscle is the source of cues that determine the central connections of the sensory neurons projecting to it. Motoneurons forced to innervate novel muscle received many of the same sensory inputs they would normally receive, suggesting that motoneurons are less influenced by their target tissue than sensory neurons.
通过对鸡胚进行操作，使感觉神经元为大腿背侧肌肉的重复肌群提供神经支配，以此来研究决定肌肉感觉神经元中枢连接的环境线索来源。这些神经元沿着腹侧神经通路并伴随运动轴突投射，这些运动轴突通常投射到腹侧肌肉，但它们最终的靶组织却是背侧肌肉的重复肌群。随后，在分离的脊髓标本中通过细胞内记录来确定这些感觉神经元与支配正常背侧肌肉的运动神经元之间的中枢连接。为单个重复背侧肌肉提供神经支配的感觉神经元与为相应正常背侧肌肉提供神经支配的感觉神经元建立了相同的连接；这些连接模式与为腹侧肌肉提供传入神经的连接模式不同。因此，感觉神经元建立的突触连接与其靶肌肉相适应，而非与其更靠近腹侧的环境相适应。这些发现表明，靶肌肉是决定投射到其上的感觉神经元中枢连接的线索来源。被迫支配新肌肉的运动神经元接收到许多它们正常情况下会接收到的相同感觉输入，这表明运动神经元受其靶组织的影响小于感觉神经元。
