The antagonistic effect of the sigma 1 receptor ligand (+)-MR200 on persistent pain induced by inflammation.

OBJECTIVE AND DESIGN: The sigma 1 (σ1) receptor, which is widely distributed inthe CNS in areas that are known to be important for pain control, may play a rolein persistent pain characterized by the hypersensitivity of nociceptivetransmission. Here, we investigated the effect of σ1 blockade in an inflammatory pain model.TREATMENT AND METHODS: An intraplantar injection of carrageenan (2 %) was used toinduce paw inflammation. The effects of the σ1 antagonist (+)-MR200, givensubcutaneously at a dose of 0.1, 0.25, 0.5,1, 1.5, and 2 mg/kg prior to injectionof carrageenan, on inflammatory pain and inflammation were assessed. Mechanicalallodynia with von Frey filaments, thermal hyperalgesia with the plantar test andedema evaluation with a plethysmometer were measured. Intergroup comparisons wereassessed by one- or two-way analysis of variance when appropriate, followed bypost-hoc tests (Dunnett's test for one-way or Bonferroni for two-way ANOVA).RESULTS: (+)-MR200 dose-dependently prevented allodynia and hyperalgesia induced by carrageenan. Furthermore, it reduced paw edema with a significant inhibitionpercentage of 37.82 % at 3 h after carrageenan treatment.CONCLUSIONS: The blockade of the σ1 receptor with the selective antagonist(+)-MR200 may contribute to the suppression of the typical symptoms ofinflammatory pain.