Experimental study of central nervous modulation of the temporomandibular joint disorder associated with malocculusion

正畸牙齿移动会引起疼痛和不适。当正畸力施加到牙齿上时，牙周组织内会发生炎症事件，物质会释放出来，这可能与痛感的机制有关。即刻早期基因c-fos编码核蛋白Fos。突触激活后脑内Fos的诱导是神经元特有的，c-fos的激活被报道为脑内神经突触路径追踪的代谢标记物。采用Fos免疫组织化学方法，观察实验性牙齿移动对大鼠脑内c-fos表达的影响。在大鼠上磨牙间一侧插入正畸弹性模块。实验牙齿移动24小时后，Fos免疫反应阳性神经元出现在同侧三叉神经尾侧亚核和双侧臂旁外侧核，已知参与伤害性信息的传递。实验性牙齿移动后，大鼠前脑杏仁中央核(ACE)、下丘脑室旁核(PVH)和丘脑室旁核(PV)出现Fos样免疫反应神经元。与假手术对照组相比，血管紧张素转换酶同侧和对侧分别增加639%和644%，PVH同侧和对侧分别增加292%和307%，PV增加264%。这些结果表明，实验性牙齿移动引起的伤害性信息可能由中枢神经系统的多个区域传递和调制。

Orthodontic tooth movement induces pain and discomfort. When an orthodontic force is applied to teeth, an inflammatory event occurs within the periodontium and substances are released, which could be related to the mechanism of pain sensation. Immediate early gene, c-fos, encodes the nuclear protein Fos. The induction of Fos in the brain following synaptic activation is specific for neurons, and c-fos activation has been reported to be utilized as a metabolic maker for neurosynaptic pathway tracing in the brain. We investigated the effect of experimental tooth movement on the c-fos expression in the rat brain by using Fos immunohistochemistry. An orthodontic elastic module was unilaterally inserted between upper molars of rats. Twenty-four hours after the commencement of the experimental tooth movement, Fos-like immunoreactive neurons appeared ipsilaterally in the trigeminal subnucleus caudalis and bilaterally in the lateral parabrachial nucleus, which is known to be involved in transmission of the nociceptive information. Following experimental tooth movement, the Fos-like immunoreactive neurons appeared in the central nucleus of the amygdala (ACE), paraventricular nucleus of the hypothalamus (PVH) and paraventricular nucleus of the thalamus (PV) of the experimental rat forebrain. The numbers of the labeled neurons were significantly increased by 639% and 644% in the ipsilateral and contralateral side of ACE respectively, by 292% and 307% in the ipsilateral and contralateral side of PVH,and by 264% in the PV with respect to sham control rats. These results suggest that nociceptive information caused by experimental tooth movement might be transmitted and modulated by several regions of the central nervous system.