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 in the CNS in areas that are known to be important for pain control, may play a role in persistent pain characterized by the hypersensitivity of nociceptive transmission. Here, we investigated the effect of σ1 blockade in an inflammatory pain model.

TREATMENT AND METHODS

An intraplantar injection of carrageenan (2 %) was used to induce paw inflammation. The effects of the σ1 antagonist (+)-MR200, given subcutaneously at a dose of 0.1, 0.25, 0.5,1, 1.5, and 2 mg/kg prior to injection of carrageenan, on inflammatory pain and inflammation were assessed. Mechanical allodynia with von Frey filaments, thermal hyperalgesia with the plantar test and edema evaluation with a plethysmometer were measured. Intergroup comparisons were assessed by one- or two-way analysis of variance when appropriate, followed by post-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 inhibition percentage 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 of inflammatory pain.