Alterations in expression of neuropeptide gene in trigeminal ganglion in orthodontic tooth movement

本研究旨在探讨正畸牙移动初期疼痛的机制及正畸牙齿移动对中枢神经系统的影响。首先，本实验观察了大鼠实验性牙齿移动过程中三叉神经节内含Corp的牙周神经纤维和CGRP阳性神经元分布的变化。同时，用免疫组织化学方法检测牙周细胞中热休克蛋白(HSP)免疫反应阳性神经元的表达，以证实牙周应激参与牙周膜CGRP免疫反应(-IR)神经的改变，并观察三叉神经尾侧亚核Fos样免疫反应神经元分布的时程变化。结果如下：1.牙齿移动后1h，三叉神经节内CGRP免疫反应阳性神经元数量开始减少，3h达到最低值。随后，CGRP免疫反应阳性神经元数量持续增加，直至12h。最后，在对照组和实验组之间，显示CGRP免疫反应的神经元数量没有显著差异。另一方面，从牙齿移动6h开始，PDL内的CGRP-IR神经呈轻微增加趋势。部分牙周成纤维细胞在牙齿移动后1h开始表达HSP60免疫反应。HSP-60-IR细胞数量持续增加，至12h后逐渐减少。三叉神经尾侧亚核Fos-IR神经元数量在牙齿移动后1~4h显著增加，2小时达到高峰，以后逐渐减少，提示正畸牙移动可能引起三叉神经尾侧亚核的应激反应，正畸牙齿移动引起的伤害性刺激可能通过分布于三叉神经尾侧亚核的神经影响三叉神经节和三叉神经尾侧亚核。

In this study, the following experiments were performed to investigate the mechanism of pain in the initial stage of orthodontic tooth movement and influences of orthodontic tooth movement on the CNS.First, the change in the distribution of periodontal nerve fibers containing CORP and CGRP-positive neurons in the trigeminal ganglion during experimental tooth movement were observed in the same rat. Simultaneously, the expression of Heat Shock Protein (HSP)-immunoreactivity in the periodontal cells was also immunohistochemically examined to demonstrate the involvement of peridontal stress in alterations of CGRP-immunoreactive (-IR) nerves in PDL.Furthermore, the temporal changes in the distribution of Fos-like-IR neurons in the trigeminal subnucleus caudalis was investigated. The following results were obtained :1. At 1hour of tooth movement, the number of CGRP-IR neurons in the trigeminal ganglion began to decrease and reached minimum at 3 hours. Then, the number of CGRP-IR neurons persisted to increase inversly until 12 hours. Finally, no significant difference in the number of neurons showing CGRP-immunoreactivity was recognized between control and experimental groups. On the other hand, CGRP-IR nerves in the PDL showed a tendency to increase slightly from 6 hours of tooth movement.2. Some peridontal fibroblasts began to show HSP 60-immnoreactivity from 1 hour of tooth movement. The number of HSP-60-IR cells continued to increase until 12 hours, and then decreased gradually.3. The number of Fos-IR neurons in the trigeminal subnucleus caudalis increased significantly from 1 to 4 hours of tooth movement, reaching maximum at 2 hours, and then decreased by degrees.These findings suggest that orthodontic tooth movement may cause the stress reaction in the PDL, and that the nociceptive stimuli evoked by orthodontic tooth movement may affect the trigeminal ganglion and the trigeminal subnucleus caudalis through the nerves distributed in the PDL.