Ishihara A, Roy R R, Edgerton V R
Department of Physiological Science, University of California, Los Angeles 90095, USA.
Neuroscience. 1995 Oct;68(3):813-22. doi: 10.1016/0306-4522(95)00165-f.
The spatial distribution, soma size and oxidative enzyme activity of gamma and alpha motoneurons innervating muscle fibres in the deep (away from the surface of the muscle) and superficial (close to the surface of the muscle) portions of the tibialis anterior in normal rats were determined. The deep portion had a higher percentage of high oxidative fibres than the superficial portion of the muscle. Motoneurons were labelled by retrograde neuronal transport of fluorescent tracers: Fast Blue and Nuclear Yellow were injected into the deep portion and Nuclear Yellow into the superficial portion of the muscle. Therefore, motoneurons innervating the deep portion were identified by both a blue fluorescent cytoplasm and a golden-yellow fluorescent nucleus, while motoneurons innervating the superficial portion were identified by only a golden-yellow fluorescent nucleus. After staining for succinate dehydrogenase activity on the same section used for the identification of the motoneurons, soma size and succinate dehydrogenase activity of the motoneurons were measured. The gamma and alpha motoneurons innervating both the deep and superficial portions were located primarily at L4 and were intermingled within the same region of the dorsolateral portion of the ventral horn in the spinal cord. Mean soma size was similar for either gamma or alpha motoneurons in the two portions of the muscle. The alpha motoneurons innervating the superficial portion had a lower mean succinate dehydrogenase activity than those innervating the deep portion of the muscle. An inverse relationship between soma size and succinate dehydrogenase activity of alpha, but not gamma, motoneurons innervating both the deep and superficial portions was observed. Based on three-dimensional reconstructions within the spinal cord, there were no apparent differences in the spatial distribution of the motoneurons, either gamma or alpha, associated with the deep and superficial compartments of the muscle. The data provide evidence for an interdependence in the oxidative capacity between a motoneuron and its target muscle fibres in two subpopulations of motoneurons from the same motor pool, i.e. the same muscle.
测定了正常大鼠胫前肌深层（远离肌肉表面）和浅层（靠近肌肉表面）部分中支配肌纤维的γ运动神经元和α运动神经元的空间分布、胞体大小及氧化酶活性。深层部分的高氧化纤维百分比高于肌肉的浅层部分。通过荧光示踪剂的逆行神经元运输对运动神经元进行标记：将快蓝和核黄注入肌肉深层部分，将核黄注入肌肉浅层部分。因此，支配深层部分的运动神经元通过蓝色荧光细胞质和金黄色荧光细胞核来识别，而支配浅层部分的运动神经元仅通过金黄色荧光细胞核来识别。在用于识别运动神经元的同一切片上进行琥珀酸脱氢酶活性染色后，测量运动神经元的胞体大小和琥珀酸脱氢酶活性。支配深层和浅层部分的γ运动神经元和α运动神经元主要位于L4，并且在脊髓腹角背外侧部分的同一区域内相互交织。肌肉两部分中γ或α运动神经元的平均胞体大小相似。支配浅层部分的α运动神经元的平均琥珀酸脱氢酶活性低于支配肌肉深层部分的α运动神经元。观察到支配深层和浅层部分的α运动神经元（而非γ运动神经元）的胞体大小与琥珀酸脱氢酶活性之间呈负相关。基于脊髓内的三维重建，与肌肉深层和浅层隔室相关的γ或α运动神经元在空间分布上没有明显差异。这些数据为来自同一运动池（即同一块肌肉）的两个运动神经元亚群中运动神经元与其靶肌纤维之间氧化能力的相互依赖性提供了证据。
