1,8-cineole decreases neuropathic pain probably via a mechanism mediating P2X3 receptor in the dorsal root ganglion.

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.