Oka Y, Ohtani R, Satou M, Ueda K
Zoological Institute, Faculty of Science, University of Tokyo, Japan.
J Comp Neurol. 1989 Aug 15;286(3):376-83. doi: 10.1002/cne.902860307.
To label the spinal motoneurons innervating the forelimb muscles of the Japanese toad, horseradish peroxidase (HRP) was injected into these muscles or applied to the cut end of the brachial nerves (N. radialis and N. ulnaris). Spatial distribution of the HRP-labeled motoneurons was reconstructed from serial frontal sections of the spinal cord and their location was examined. Motoneurons innervating forelimb muscles were distributed in the lateral cell column from segment 3 to segment 5 of the ipsilateral brachial spinal cord. In the transverse plane of the spinal cord, motoneurons innervating the medial forearm muscles (innervated by N. ulnaris) were located in the more medial part of the lateral cell column, whereas those innervating the lateral forearm muscles and the upper arm muscle (innervated by N. radialis) were located in the more lateral part of the lateral cell column. Along the longitudinal axis of the spinal cord, motoneurons innervating the more anterior (flexor side) forearm muscles were located in the more rostral part of the spinal cord, whereas those innervating the more posterior (extensor side) forearm muscles were located in the more caudal part of the spinal cord. Thus, motoneurons innervating forearm muscles were well organized somatotopically not only in the transverse plane, but also along the longitudinal axis of the spinal cord. Such a somatotopic organization of motoneurons along the longitudinal axis could also be regarded as a functional one; the flexor motoneurons were located rostrally to the extensor motoneurons.
为标记支配日本蟾蜍前肢肌肉的脊髓运动神经元，将辣根过氧化物酶（HRP）注入这些肌肉或应用于臂神经（桡神经和尺神经）的切断端。从脊髓连续额状切片重建HRP标记运动神经元的空间分布并检查其位置。支配前肢肌肉的运动神经元分布在同侧臂脊髓第3节段至第5节段的外侧细胞柱中。在脊髓横切面上，支配前臂内侧肌肉（由尺神经支配）的运动神经元位于外侧细胞柱的更内侧部分，而支配前臂外侧肌肉和上臂肌肉（由桡神经支配）的运动神经元位于外侧细胞柱的更外侧部分。沿脊髓纵轴，支配前臂更靠前（屈肌侧）肌肉的运动神经元位于脊髓的更靠前部分，而支配前臂更靠后（伸肌侧）肌肉的运动神经元位于脊髓的更靠后部分。因此，支配前臂肌肉的运动神经元不仅在横切面上，而且沿脊髓纵轴都有良好的躯体定位组织。这种沿纵轴的运动神经元躯体定位组织也可被视为一种功能组织；屈肌运动神经元位于伸肌运动神经元的前方。
