Department of Cell Biology, University of Basel, Biozentrum, Klingelbergstrasse 70, 4056 Basel, Switzerland.
Neuron. 2010 Nov 4;68(3):456-72. doi: 10.1016/j.neuron.2010.10.019.
Movement is the behavioral output of neuronal activity in the spinal cord. Motor neurons are grouped into motor neuron pools, the functional units innervating individual muscles. Here we establish an anatomical rabies virus-based connectivity assay in early postnatal mice. We employ it to study the connectivity scheme of premotor neurons, the neuronal cohorts monosynaptically connected to motor neurons, unveiling three aspects of organization. First, motor neuron pools are connected to segmentally widely distributed yet stereotypic interneuron populations, differing for pools innervating functionally distinct muscles. Second, depending on subpopulation identity, interneurons take on local or segmentally distributed positions. Third, cholinergic partition cells involved in the regulation of motor neuron excitability segregate into ipsilaterally and bilaterally projecting populations, the latter exhibiting preferential connections to functionally equivalent motor neuron pools bilaterally. Our study visualizes the widespread yet precise nature of the connectivity matrix for premotor interneurons and reveals exquisite synaptic specificity for bilaterally projecting cholinergic partition cells.
运动是脊髓神经元活动的行为输出。运动神经元被分组为运动神经元池，它们是支配单个肌肉的功能单位。在这里，我们在新生小鼠中建立了一种基于狂犬病病毒的解剖连接测定法。我们利用它来研究运动前神经元的连接模式，即与运动神经元单突触连接的神经元群，揭示了组织的三个方面。首先，运动神经元池与节段性广泛分布但具有刻板印象的中间神经元群相连，这些神经元群因支配功能不同的肌肉而不同。其次，根据亚群的身份，中间神经元占据局部或节段性分布的位置。第三，参与调节运动神经元兴奋性的胆碱能分隔细胞分为同侧和双侧投射群体，后者表现出对双侧功能等效的运动神经元池的优先连接。我们的研究可视化了运动前中间神经元连接矩阵的广泛而精确的性质，并揭示了双侧投射胆碱能分隔细胞的高度特异性突触。
