Shigenaga Y, Sera M, Nishimori T, Suemune S, Nishimura M, Yoshida A, Tsuru K
Department of Oral Anatomy (1st Division), Hiroshima University School of Dentistry, Japan.
J Comp Neurol. 1988 Feb 22;268(4):489-507. doi: 10.1002/cne.902680403.
Retrograde and anterograde transport of horseradish peroxidase-wheat germ agglutinin (HRP-WGA) conjugate was used to study the organization of primary afferent neurons innervating the masticatory muscles. HRP applied to the nerves of jaw-closing muscles--the deep temporal (DT), masseter (Ma), and medial pterygoid (MP)--labeled cells in the trigeminal ganglion and the mesencephalic trigeminal nucleus (Vmes), whereas HRP applied to nerves of the jaw-opening muscles--anterior digastric (AD) and mylohyoid (My)--labeled cells only in the trigeminal ganglion. Cell bodies innervating the jaw-closing muscles were found with greater frequency in the intermediate region of the mandibular subdivision, while somata supplying the jaw-opening muscles were predominant posterolaterally. The distribution of their somatic sizes was unimodal and limited to a subpopulation of smaller cells. Projections of the muscle afferents of ganglionic origin to the trigeminal sensory nuclear complex (TSNC) were confined primarily to the caudal half of pars interpolaris (Vi), and the medullary and upper cervical dorsal horns. In the Vi, Ma, MP, AD, and My nerves terminated in the lateral-most part of the nucleus with an extensive overlap in projections, save for the DT nerve, which projected to the interstitial nucleus or paratrigeminal nucleus. In the medullary and upper cervical dorsal horns, the main terminal fields of individual branches were confined to laminae I/V, but the density of the terminals in lamina V was very sparse. The rostrocaudal extent of the terminal field in lamina I differed among the muscle afferents of origin, whereas in the mediolateral or dorsoventral axis, a remarkable overlap in projections was noted between or among muscle afferents. The terminals of DT afferents were most broadly extended from the rostral level of the pars caudalis to the C3 segment, whereas the MP nerve showed limited projection to the middle one-third of the pars caudalis. Terminal fields of the Ma, AD, and My nerves appeared in the caudal two-thirds of the pars caudalis including the first two cervical segments, the caudal half of the pars caudalis and the C1 segment, and in the caudal part of the pars caudalis including the rostral C1 segment, respectively. This rostrocaudal arrangement in the projections of muscle nerves, which corresponds to the anteroposterior length of the muscles and their positions, indicates that representation of the masticatory muscles in lamina I reflects an onion-skin organization. These results suggest that primary muscle afferent neurons of ganglionic origin primarily mediate muscle pain.(ABSTRACT TRUNCATED AT 400 WORDS)
采用辣根过氧化物酶-小麦胚凝集素（HRP-WGA）复合物的逆行和顺行运输来研究支配咀嚼肌的初级传入神经元的组织。将HRP应用于闭口肌神经——颞深肌（DT）、咬肌（Ma）和翼内肌（MP）——标记三叉神经节和三叉神经中脑核（Vmes）中的细胞，而将HRP应用于开口肌神经——二腹肌前腹（AD）和下颌舌骨肌（My）——仅标记三叉神经节中的细胞。支配闭口肌的细胞体在下颌支的中间区域更为常见，而供应开口肌的细胞体主要位于后外侧。它们的体细胞大小分布是单峰的，且仅限于较小细胞的亚群。神经节起源的肌肉传入纤维向三叉神经感觉核复合体（TSNC）的投射主要局限于极间部（Vi）的后半部、延髓和上颈段背角。在Vi中，Ma、MP、AD和My神经在核的最外侧终止，投射有广泛重叠，但DT神经投射到间质核或三叉旁核。在延髓和上颈段背角，各分支的主要终末场局限于I/V层，但V层的终末密度非常稀疏。I层终末场的 rostrocaudal范围在不同起源的肌肉传入纤维中有所不同，而在内外侧或背腹轴上，肌肉传入纤维之间或之中的投射有明显重叠。DT传入纤维的终末从尾侧部的头侧水平延伸到C3节段最为广泛，而MP神经向尾侧部的中间三分之一的投射有限。Ma、AD和My神经的终末场分别出现在尾侧部的后三分之二包括前两个颈段、尾侧部的后半部和C1节段，以及尾侧部的尾侧部分包括头侧C1节段。肌肉神经投射中的这种 rostrocaudal排列，与肌肉的前后长度及其位置相对应，表明I层中咀嚼肌的代表反映了洋葱皮样组织。这些结果表明，神经节起源的初级肌肉传入神经元主要介导肌肉疼痛。（摘要截短于400字）
