Antinociceptive mechanisms of Rosmarinus officinalis extract in mice using writhing test

Rosemary (Rosmarinus officinalis) is a common household plant grows in many parts of the world, including Iran. Rosemary leaves are used in folk medicine as an antispasmodic, analgesic, diuretic and antiepileptic agent. The objective of this study was to investigate the antinociceptive mechanisms of rosemary extract using a writhing test as a model of visceral pain. Possible antinociceptive mechanisms were explored by testing the effects of naloxone (nonselective opioid antagonist), cyproheptadine (nonselective serotonin antagonist), Chicago sky blue 6B (inhibitor of glutamate uptake) and bicuculline (GABAA antagonist) on rosemary extract-induced antinociception. Results showed that rosemary extract (50, 100 and 200 mg/kg, i.p.) induces antinociceptive effects in a dose-dependent manner (p< .001). Pre-treatment with naloxone and bicuculline significantly reduced this effect (from 61.04% to 27.56%, and from 60.31% to 42.09%, respectively; p<0.05). Naloxone and bicuculline brought forward the onset of first abdominal writhing in comparison with extract (p< .001). The analgesic effect and latency induced by the extract significantly increased with Chicago sky blue 6B pre-treatment (p<0.05), while cyproheptadine had no effect. These results indicate that the antinociceptive effect of Rosmarinus officinalis may be mediated by opioidergic, glutamatergic and GABAergic mechanisms.