Lipski J, Martin-Body R L
J Comp Neurol. 1987 Jun 15;260(3):423-34. doi: 10.1002/cne.902600308.
This study was undertaken to describe details of the location and cellular morphology of functionally identified (inspiratory or expiratory) external and internal intercostal motoneurons on the basis of intracellular injection of horseradish peroxidase (HRP). Sixty HRP-labeled motoneurons were examined; 44 in transverse, 16 in sagittal sections. In the upper thoracic segments (T3-T4), there was only a small overlap in the location of inspiratory external and internal intercostal motoneurons; the inspiratory external motoneurons were generally found more ventromedially within the ventral horn than either inspiratory or expiratory internal intercostal motoneurons. No major morphological differences were observed between the types of motoneurons studied. The number of primary dendrites ranged from 6 to 10. The dendrites projected mainly along the medial or the lateral border of the ventral horn, and rostrocaudally up to 1,760 micron from the cell body. The paths taken by dendrites to fill the territory occupied by the dendritic trees appeared to depend upon location of the cell body. Few dendrites penetrated the white matter. Axon diameters varied from 1.1 to 6.7 micron (mean 3.6 +/- 1.3 micron, n = 55). Collateral branches were identified in 78% of axons. The number of branches arising from a given axon varied from 1 to 4. It is concluded that the respiratory intercostal motoneurons form a morphologically homogeneous population, in spite of their functional differences.
本研究旨在通过细胞内注射辣根过氧化物酶（HRP）来描述功能已确定（吸气或呼气）的肋间外肌和肋间内肌运动神经元的位置及细胞形态细节。共检查了60个HRP标记的运动神经元；其中44个在横切面上，16个在矢状切面上。在上胸部节段（T3 - T4），吸气性肋间外肌和肋间内肌运动神经元的位置仅有少量重叠；吸气性肋间外肌运动神经元通常比吸气性或呼气性肋间内肌运动神经元更靠近腹角的腹内侧。在所研究的运动神经元类型之间未观察到主要的形态学差异。初级树突的数量范围为6至10个。树突主要沿腹角的内侧或外侧边缘投射，从细胞体向头尾方向延伸可达1760微米。树突填充树突野所采取的路径似乎取决于细胞体的位置。很少有树突穿透白质。轴突直径从1.1至6.7微米不等（平均3.6 +/- 1.3微米，n = 55）。78%的轴突有侧支。给定轴突发出的分支数量从1至4个不等。结论是，尽管呼吸性肋间运动神经元存在功能差异，但它们在形态上构成一个同质群体。
