Ro Jin Y, Harriott Andrea, Crouse Ulla, Capra Norman F
Department of Oral and Craniofacial Biological Sciences, University of Maryland Baltimore School of Dentistry, 666 W. Baltimore Street, Baltimore, MD 21201, USA.
Pain. 2003 Aug;104(3):539-548. doi: 10.1016/S0304-3959(03)00093-9.
Muscle tenderness and pain during movements are prominent symptoms associated with persistent jaw muscle pain. However, there is virtually no information on how trigeminal neurons respond to jaw movements (JM) or muscle palpation in the presence of muscle tissue injury or myositis. In this study, we investigated the effects of innocuous JM in the presence of acute masseteric inflammation on postsynaptic responses in the trigeminal brainstem nuclei by examining the expression of c-fos. In one group of rats, unilateral injections of an inflammatory substance, mustard oil (MO: 20%, 25 microl) were made into a masseter muscle. In another group, controlled and systematic JM were provided following MO injection. Three additional groups of rats were used to control for anesthetic, JM, and injection procedure. MO injected in the masseter muscle induced a high level of Fos protein expression in four principal trigeminal regions: the subnucleus caudalis (Vc), the ventral and dorsal regions of the Vc/Vi (subnucleus interpolaris) transition zone, and the paratrigeminal nucleus (PTN). Movements following MO injection consistently produced a significantly greater level of Fos expression in all these areas, especially in the Vc/Vi transition region and caudal Vc on the ipsilateral side. Importantly, movements also induced a significantly greater level of Fos expression in the caudal Vc on the contralateral side. The present results provide the first documentation that innocuous JM in the presence of muscle inflammation significantly increase the MO-induced c-fos expression in the trigeminal brainstem nuclei, which may explain the greater pain experienced during movement of inflamed or injured muscles.
运动时肌肉压痛和疼痛是与持续性颌面部肌肉疼痛相关的突出症状。然而，在存在肌肉组织损伤或肌炎的情况下，关于三叉神经元如何对颌面部运动（JM）或肌肉触诊做出反应，几乎没有相关信息。在本研究中，我们通过检测c-fos的表达，研究了在急性咬肌炎症存在时无害的JM对三叉神经脑干核中突触后反应的影响。在一组大鼠中，将炎性物质芥子油（MO：20%，25微升）单侧注射到咬肌中。在另一组中，在注射MO后进行有控制的、系统性的JM。另外三组大鼠用于控制麻醉、JM和注射程序。注射到咬肌中的MO在四个主要三叉神经区域诱导了高水平的Fos蛋白表达：尾侧亚核（Vc）、Vc/Vi（极间亚核）过渡区的腹侧和背侧区域以及三叉旁核（PTN）。注射MO后的运动在所有这些区域始终产生显著更高水平的Fos表达，尤其是在同侧的Vc/Vi过渡区和尾侧Vc。重要的是，运动在对侧尾侧Vc中也诱导了显著更高水平的Fos表达。目前的结果首次证明，在存在肌肉炎症时无害的JM会显著增加MO诱导的三叉神经脑干核中c-fos的表达，这可能解释了在发炎或受伤肌肉运动期间经历的更剧烈疼痛。
