Paik S K, Park K P, Lee S K, Ma S K, Cho Y S, Kim Y K, Rhyu I J, Ahn D K, Yoshida A, Bae Y C
Department of Oral Anatomy and Neurobiology, BK21, School of Dentistry, Kyungpook National University, 188-1, 2-Ga, Samdeok-dong, Jung-Gu, Daegu 700-412, South Korea.
Neuroscience. 2009 Sep 15;162(4):1279-86. doi: 10.1016/j.neuroscience.2009.05.046. Epub 2009 May 27.
The morphology of intradental nerve fibers of permanent teeth and of continuously growing rodent incisors has been studied in detail but little information is available on the parent axons that give rise to these fibers. Here we examined the axons and somata of trigeminal neurons that innervate the rat upper molar and lower incisor pulp using tracing with horseradish peroxidase and light and electron microscopic analysis. The majority (approximately 80%) of the parent axons in the proximal root of the trigeminal ganglion that innervated either molar or incisor pulp were small myelinated fibers (<20 microm(2) cross-sectional area). The remaining approximately 20% of the fibers were almost exclusively large myelinated for the molar pulp and unmyelinated for the incisor pulp. The majority of neuronal somata in the trigeminal ganglion that innervated either molar (48%) or incisor pulp (62%) were medium in size (300-600 microm(2) cross-sectional area). Large somata (>600 microm(2)) constituted 34% and 20% of the trigeminal neurons innervating molar and incisor pulp, respectively, while small somata (<300 microm(2)) constituted 17% of the molar and 18% of the incisor neurons. The present study revealed that the morphology of parent axons of dental primary sensory neurons may differ from that of their intradental branches, and also suggests that the nerve fiber function may be carried out differently in the molar and incisor pulp in the rat.
恒牙和不断生长的啮齿动物门齿的牙内神经纤维形态已得到详细研究，但关于产生这些纤维的母轴突的信息却很少。在此，我们使用辣根过氧化物酶示踪以及光镜和电镜分析，研究了支配大鼠上颌磨牙和下颌门齿牙髓的三叉神经元的轴突和胞体。支配磨牙或门齿牙髓的三叉神经节近端根中的大多数母轴突（约80%）是小的有髓纤维（横截面积<20平方微米）。其余约20%的纤维，对于磨牙牙髓几乎全是大的有髓纤维，而对于门齿牙髓则是无髓纤维。支配磨牙（48%）或门齿牙髓（62%）的三叉神经节中的大多数神经元胞体大小中等（横截面积300 - 600平方微米）。大的胞体（>600平方微米）分别占支配磨牙和门齿牙髓的三叉神经元的34%和20%，而小的胞体（<300平方微米）分别占支配磨牙神经元的17%和支配门齿神经元的18%。本研究表明，牙齿初级感觉神经元的母轴突形态可能与其牙内分支的形态不同，并且还表明在大鼠中，磨牙和门齿牙髓的神经纤维功能可能以不同方式进行。
