Antihyperalgesic effects of myrsinoic acid B in pain-like behavior induced by inflammatory and neuropathic pain models in mice.

Background: Myrsinoic acid B (MAB) is a diprenylated benzoic acid widely found in the vegetal kingdom. Recent studies demonstrate that MAB has important antinociceptive effects in models of chemically or thermally induced nociception in mice.

Methods: In the present study we evaluated the effect of MAB in different models of inflammatory and neuropathic hypersensitivity in mice.

Results: This study demonstrates that the pretreatment with MAB, given orally (8.4 to 83.8 μmol/kg), inhibited carrageenan- and complete Freund adjuvant-induced mechanical hypersensitivity. When administered after the induction of hypersensitivity, MAB also reduced the mechanical hypersensitivity in the ipsilateral and in the contralateral hindpaws of mice injected with complete Freund adjuvant, interfering with a signaling cascade already established. MAB reversed the hypersensitivity (mechanical and thermal) of operated animals, with similar results to those observed with gabapentin. MAB activity was evident when administered either systemically (PO or IV) or intrathecally, suggesting interference in the central pathways of pain control. Furthermore, MAB seems to present an antiinflammatory effect evidenced by the interference in both the neutrophil migration and in the increase of interleukin-1β levels after carrageenan injection. Of note, MAB treatment did not interfere with mechanical or thermal sensitivity in healthy mice, a frequent characteristic of commonly used analgesics, such as morphine or gabapentin. Side effects including interference in locomotor activity, motor performance, and body temperature in animals treated with MAB were absent.

Conclusions: MAB reduced mechanical and thermal hypersensitivity in mice submitted to models of inflammatory and neuropathic pain, showing excellent potential for treating persistent pain in humans.