Antinociceptive effects of methyl jasmonate in experimental animals.

Methyl jasmonate (MJ) is a chemical compound that has been postulated to play a role in plant wound and pathogen responses. While the anti-inflammatory property of MJ has been reported in literature, no studies have been carried out to describe its role in the modulation of pain. Thus, this present investigation sought to evaluate the antinociceptive activity of MJ in animal models of pain. The antinociceptive activity of MJ (10-50 mg/kg) administered intraperitoneally (i.p.) was screened using the acetic acid-induced writhing, tail immersion, formalin-induced paw licking and Randall-Selitto paw pressure tests in rodents. MJ demonstrated inhibitory activity against acetic acid-induced abdominal constrictions in mice. It further produced a significant suppression of the inflammatory pain associated with the second phase of the formalin test in mice. However, MJ did not inhibit the neurogenic pain associated with the first phase of the formalin test and also failed to alter the reaction time of mice to noxious heat in the tail immersion test. In the Randall-Selitto paw pressure test, MJ significantly prolonged the paw withdrawal latency in the inflamed hind paw but did not alter the pain response in the non-inflamed hind paw of rats. The acute toxicity test showed that MJ given i.p. was well tolerated by the animals, as no toxic symptoms or death were observed at a dose range of 100-300 mg/kg in mice. Behavioural changes (ataxia, sedation and hyperventilation) were only observed at higher doses of MJ (400 and 500 mg/kg). Taken together, these findings suggest that methyl jasmonate has antinociceptive activity and may serve as a therapeutic in the treatment of inflammatory pain.