雌激素对女性颞下颌关节紊乱病（TMD）的咀嚼肌痛和颞下颌关节（TMJ）痛的影响一直存在争论，且这类疼痛缺乏有效的治疗方法。雌激素水平持续提高可能是该病促进因素之一，但动物实验结论不一致。动物研究发现雌激素水平升高能增加咬肌伤害感受器对NMDA 受体兴奋剂的敏感度，理论上植物雌激素能通过降低雌激素效应的周期性波动幅度来治疗疼痛。本研究假设：快速与稳定升高雌激素浓度都能增加雌性大鼠咀嚼肌与关节的伤害感受器对机械和化学刺激的敏感度；染料木素（大豆植物雌激素）能影响此效应。研究采用去卵巢大鼠给与雌激素和染料木素，通过机械痛阈、免疫组化、蛋白定量手段，分析雌激素快速或持续升高时咀嚼肌对机械和化学疼痛刺激的反应，以及染料木素对这类疼痛的影响。大豆植物雌激素安全性高，用于治疗口面痛有新意。本研究结论可用来探索植物雌激素治疗TMD 疼痛的临床试验。

There are considerable controversies about the role of the estrogen in the pain in the masticatory muscle and temporomandibular joint (TMJ) of women with temporomandibular disorders (TMD) and the available treatment for such pain is ineffective. Continuing increase of estrogen level may be one of the promoting factors, but there is no consistent conclusion based on animal experiments. Previous animal studies indicate that increased serum levels of estrogen are associated with increased sensitivity of masseter muscle nociceptors to NMDA receptor agonists. Soy isoflavanoids are weak plant estrogens (phytoestrogens) that can act as estrogen receptor agonists when estrogen levels are low and as estrogen receptor antagonists when estrogen levels are elevated. Theoretically, phytoestrogens could act by reducing the magnitude of fluctuations in estrogenic effect over the menstrual cycle and this may lead to their potential effect of ameliorating pain in conditions such as TMD. Therefore, one objective of this proposal is to test the concept that both rapid and sustained elevations of estrogen concentration will increase the mechanical and chemical sensitivity of nociceptors of jaw-muscles in female rats. Another objective of this proposal is to investigate how genistein, a plant phytoestrogen, modifies the effects of estrogen on the sensitivity of jaw-muscle nociceptors in rats. Estrogen or genistein will be administered in ovariectomized rats. Behavioral testing of mechanical hyperalgesia, immunohistochemistry, and western blotting will be used to examine the response properties of nociceptors of masticatory muscle and joint to mechanical and chemical stimulus. The proposed research will help to illustrate how estrogen modulates pain transduction in jaw-muscles and whether a phytoestrogen can significantly modify the effects of estrogen. It is high-safe and novel to intervene orofacial pain with phytoestrogens. Results of the proposed studies could be translated into future clinical studies to investigate the efficacy of phytoestrogens for the alleviation of TMD-related pain.

颞下颌关节紊乱病（TMDs）主要侵犯育龄期女性，疼痛为其主要症状。尽管TMDs流行的性别差异有多种解释，一个可能的原因被认为与性激素有关。染料木素（genistein，Gen）是大豆异黄酮苷元中的主要成分，其结构与雌激素相似，是弱的植物雌激素，当雌激素水平低时能作为雌激素受体的激动剂，当雌激素水平高时则成为雌激素受体的拮抗剂。本研究探索了雌二醇(E2)对咀嚼肌痛敏的影响，以及此类痛敏是否受染料木素的影响。通过大鼠咬肌注射谷氨酸（Glu）,建立咬肌疼痛模型。24只雌性大鼠卵巢切除后随机分成4组（6只/组），分别于每日皮下注射0μg, 20μg, 80μg, 200μg E2,连续10天，第11天所有大鼠咬肌注射Glu。为了研究是否Gen可以影响E2对Glu诱导的咬肌机械痛敏，48只大鼠卵巢切除后，随机分成8组（6只/组）：无处理组，Gen溶媒 + E2溶媒组，Gen溶媒 + 80μg E2，Gen （2,7.5,15,30,60mg/kg）+ 80μg E2。Gen于腹部皮下注射12天。Gen注射2天后开始注射E2，最后一天所有大鼠给予 Glu 咬肌注射。用von-Frey 测痛仪检测咬肌的摆头阈值。pNR2B 或 pERK1/2两个疼痛相关蛋白作为E2和Gen对咬肌痛敏影响的评价指标，用免疫荧光观察海马CA3区神经元中pNR2B和pERK1/2 的活化程度。用Western blot 检测海马中pNR2B和pERK1/2蛋白表达水平。结果发现随着E2剂量升高，咬肌机械刺激阈值呈现剂量依赖性的下降。海马中pNR2B 和pERK1/2 的蛋白表达在 Glu 咬肌注射后显著上升，而E2替代进一步上调海马中pNR2B 和pERK1/2 的蛋白表达。7.5 和15 mg/kg Gen预处理缓解了E2介导的咬肌痛敏，7.5, 15 和 30 mg/kg Gen预处理缓解了E2加重的 Glu 诱发的咬肌机械痛敏，其中15 mg/kg Gen效果最优。15 mg/kg Gen部分拮抗了E2增强的Glu诱导海马中pNR2B 和pERK1/2 上调。结论：E2替代升高可导致去卵巢大鼠咬肌机械刺激阈值下降；一定剂量的Gen可以拮抗E2对Glu诱发的咬肌机械痛敏。研究结果为将来临床应用Gen 治疗相关慢性疼痛患者提供了实验依据。