Department of Diagnostic and Biological Sciences, University of Minnesota School of Dentistry, SE Minneapolis, MN 55455, USA.
Pain. 2013 Jul;154(7):1057-64. doi: 10.1016/j.pain.2013.03.009. Epub 2013 Mar 15.
Estrogen status and psychological stress contribute to the expression of several chronic pain conditions including temporomandibular muscle and joint disorders (TMJD). Sensory neurons that supply the temporomandibular joint (TMJ) region terminate in laminae I and V of the spinal trigeminal nucleus (Vc/C1-2 region); however, little is known about lamina-specificity and environmental influences on the encoding properties of TMJ brainstem neurons. To test the hypothesis that Vc/C1-2 neurons integrate both interoceptive and exteroceptive signals relevant for TMJ nociception, we recorded TMJ-evoked activity in superficial and deep laminae of ovariectomized rats under high and low estradiol (E2) and stress conditions. Rats received daily injections of low (LE) or high (HE) dose E2 and were subjected to forced swim (FS) or sham swim conditioning for 3days. The results revealed marked lamina-specificity in that HE rats displayed enhanced TMJ-evoked activity in superficial, but not deep, laminae independent of stress conditioning. By contrast, FS conditioned rats displayed increased background firing and TMJ-evoked activity of neurons in deep, but not superficial, laminae independent of E2 status. FS also enhanced TMJ-evoked masseter muscle activity and suggested the importance of deep dorsal horn neurons in mediating evoked jaw muscle activity. In conclusion, E2 status and psychophysical stress play a significant role in modifying the encoding properties of TMJ-responsive medullary dorsal horn neurons with a marked lamina-specificity.
雌激素水平和心理压力会导致多种慢性疼痛状况的发生，包括颞下颌肌肉和关节紊乱（TMJD）。供应颞下颌关节（TMJ）区域的感觉神经元终止于脊髓三叉神经核的 I 和 V 层（Vc/C1-2 区域）；然而，关于 TMJ 脑干神经元的编码特性及其对环境影响的了解甚少。为了验证 Vc/C1-2 神经元整合与 TMJ 伤害感受相关的内感受和外感受信号的假设，我们在高雌激素（E2）和低雌激素（E2）以及应激条件下，记录了去卵巢大鼠浅层和深层脊髓三叉神经核的 TMJ 诱发活动。大鼠每天接受低（LE）或高（HE）剂量 E2 注射，并接受强迫游泳（FS）或假游泳条件处理 3 天。结果显示出明显的层特异性，即 HE 大鼠在不受应激条件影响的情况下，浅层 TMJ 诱发活动增强，但深层 TMJ 诱发活动不变。相比之下，FS 条件处理的大鼠表现出背景放电和深层而不是浅层 TMJ 诱发活动神经元的增加，而与 E2 状态无关。FS 还增强了 TMJ 诱发的咬肌活动，表明深层背角神经元在介导诱发的下颌肌肉活动中的重要性。总之，E2 状态和心理生理应激在调节 TMJ 反应性髓质背角神经元的编码特性方面起着重要作用，且具有明显的层特异性。
