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

本研究通过以下实验探讨正畸牙齿移动初期疼痛的机制以及正畸牙齿移动对中枢神经系统的影响。首先，观察三叉神经节中含有CORP和cgrp阳性神经元的牙周神经纤维在实验性牙齿运动过程中的分布变化。同时，通过免疫组织化学检测牙周细胞中热休克蛋白（HSP）免疫反应性的表达，证实牙周应激参与了牙周细胞中cgrp免疫反应性（-IR）神经的改变。此外，我们还研究了三叉神经尾侧亚核Fos-like-IR神经元分布的时间变化。得到了以下结果：1。在牙齿运动1小时时，三叉神经节内CGRP-IR神经元数量开始减少，在3小时时达到最小。然后，CGRP-IR神经元数量持续呈负增长，直到12小时。最后，在对照组和实验组之间，显示cgrp免疫反应性的神经元数量没有显著差异。另一方面，PDL的CGRP-IR神经在牙齿运动6小时后呈现轻微增加的趋势。一些牙周成纤维细胞在牙齿运动1小时后开始表现出热休克蛋白60免疫反应性。HSP-60-IR细胞数量持续增加至12 h后逐渐减少。三叉神经尾侧亚核Fos-IR神经元数量在牙齿运动1 ~ 4小时显著增加，在运动2小时达到最大值，随后逐渐减少。上述结果提示，正畸牙齿运动可引起颞下颌颞叶的应激反应，正畸牙齿运动引起的伤害性刺激可通过分布于颞下颌颞叶的神经影响三叉神经节和三叉尾侧亚核。

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.