咬合干扰致大鼠咬肌组织蛋白基因产物及P物质表达变化

Experimental occlusal interference induces the expression of protein gene products and substance P in masseter muscles of rats

目的:通过组织学方法观察咬合干扰后大鼠咬肌组织损伤情况以及外周神经介质蛋白基因产物9.5(protein gene product 9.5,PGP9.5)和P物质(substance P,SP)在咬肌组织中表达水平的变化,探讨咬合干扰后咀嚼肌疼痛的外周机制。方法:选用雄性Sprague-Dawley大鼠15只,随机分为实验组(12只)和对照组(3只),实验组粘固0.4 mm厚度全冠制造咬合干扰,对照组模拟干扰过程不施加干扰。对照组和实验组在干扰后1、5、10、21 d(实验组每个时间点各3只)测定双侧咬肌机械刺激反应阈值。实验组动物在各时间点测试后于全麻下行心脏灌注,对照组在21 d测试完毕后全麻下行心脏灌注,取双侧咬肌组织,制备石蜡切片,对切片进行常规HE染色、抗PGP9.5和抗SP免疫组化染色。结果:施加0.4 mm咬合干扰后各时间点大鼠表现出双侧咬肌机械刺激痛觉敏感;咬肌组织经HE染色未见肌纤维损伤及炎症细胞浸润;咬合干扰后PGP9.5表达在早期增高并且持续至观察结束;SP表达在5 d时到达高峰,此后逐渐减少,观察结束时与对照组相近。结论:咬合干扰所致大鼠咬肌机械刺激痛觉敏感与肌肉损伤和炎症无直接关系;咬合干扰致大鼠咬肌机械刺激痛觉敏感的初期可能存在外周敏化机制。

Objective：To investigate the peripheral mechanism by studying the histological changes of masseter muscles using HE stains and substance P（SP） and protein gene product 9.5（PGP9.5） immunohistochemical stains.Methods： Fifteen male Sprague-Dawley were randomly assigned into occlusal interference group（n=12） and control group（n=3）.In occlusal interference group,0.4 mm thick crowns were bonded to the rats＇first molar of the maxillary.In the control group,rats were anesthetized and mouths were forced open for about 5 min but restorations were not applied.1,5,10,and 21 d after 0.4 mm occlusal alteration treatment,mechanical pain thresholds of bilateral masseter muscles were quantitatively measured by modified electronic anesthesiometer in control group and occlusal interference group.The rats were euthanized by transcardiac perfusion after deep anesthetization at different time points.The paraffin sections of masseter muscles were made and processed for HE,SP,and PGP9.5 immunohistochemical staining.Results： Decreased head withdrawal threshold to mechanical pressure was detected in masseter muscles on both sides following occlusal interference.Histological stains of masseter muscles presented intact following occlusal interference,and no inflammatory cells were observed in both sides.Intensely stained PGP9.5 was observed at 1 d in occlusal interference groups and maintained until the end of the experiment.SP expression was the most obviously increased at 5 d in both sides and gradually decreased to the level of control.Conclusion： Experimental occlusal interference-induced masticatory muscle pain is associated with peripheral sensitization of nociceptive neurons rather than muscle damage and inflammation.