Antinociception Effect and Mechanism of Ruta graveolens L. in Mice

Antinociceptive profiles of Ruta graveolens L extract were examined in ICR mice. R. graveolens L extract administered orally (200 mg/kg) showed an antinociceptive effect as measured by the tailflick and hot-plate tests and attenuated the writhing numbers in the acetic acid-induced writhing test. Cumulative nociceptive response time for intrathecal (i.t.) injection of substance P (0.7 μg) was decreased by the extract. Intraperitoneal (i.p.) pretreatment with naloxone (opioid receptor antagonist) or yohimbine (α2-adrenergic receptor antagonist) attenuated antinociceptive effect induced by the extract in the writhing test. However, methysergide (5-HT serotonergic receptor antagonist) did not affect antinociception induced by the extract in the writhing test. These results suggest that R. graveolens L extract exerts antinociceptive property in various pain models. Furthermore, this antinociceptive effect of R. graveolens L extract may be mediated by opioidergic and α2-adrenergic receptors, but not by serotonergic receptors.