1,8-cineole is a natural monoterpene cyclic ether present in eucalyptus and has been reported to exhibit anti-inflammatory and antioxidant effects. The therapeutic effects of 1,8-cineole on neuropathic pain and the molecular mechanisms of its pharmacological actions remain largely unknown. In the present study, we investigated the analgesic mechanisms of orally administered 1,8-cineole in a rat model of chronic constriction injury (CCI) and examined the drug-induced modulation of P2X3 receptor expression in dorsal root ganglia. The mechanical withdrawal threshold and thermal withdrawal latency were measured in rats to assess behavioural changes 7 and 14 days after CCI surgery. Changes in P2X3 receptor mRNA expression of L4–5 dorsal root ganglia were analysed using quantitative real-time polymerase chain reaction at the 7th and 14th postoperative day. Additionally, we examined the expression of P2X3 receptor protein in L4–5 dorsal root ganglia 7 and 14 days after surgery using immunohistochemistry and western blots. We found that 1,8-cineole can alleviate pathological pain caused by P2X3 receptor stimulation and explored new methods for the prevention and treatment of neuropathic pain.

1,8-桉树脑是存在于桉树中的天然单萜环醚，据报道具有抗炎和抗氧化作用。1,8-桉树脑对神经性疼痛的治疗作用及其药理作用的分子机制仍然未知。在本研究中，我们研究了在慢性收缩损伤（CCI）大鼠模型中口服1,8-桉树脑的镇痛机制，并研究了药物诱导的背根神经节中P2X3受体表达的调节。在大鼠中测量了机械性戒断阈值和热性戒断潜伏期，以评估CCI手术后7天和14天的行为变化。在术后第7天和第14天，采用定量实时聚合酶链反应分析L4-5背根神经节P2X3受体mRNA表达的变化。此外，我们使用免疫组织化学和免疫印迹技术在手术后第7天和第14天检查了L4-5背根神经节中P2X3受体蛋白的表达。我们发现1,8-桉树脑可以减轻由P2X3受体刺激引起的病理性疼痛，并探索了预防和治疗神经性疼痛的新方法。