Foeniculum vulgare (fennel) has been widely used in traditional medicine for treatment of various diseases including pediatric colic. This study was designed to assess the antinociceptive effects of aqueous extract of F. vulgare on visceral pain and possible involvement of opioidergic, serotonergic, adrenergic and histaminergic systems. The results of this study showed that aqueous extract of F. vulgare (50, 100 and 200 mg/kg, IP) induces antinociceptive effects (P<0.001) and that the pretreatment with chlorpheniramine and cimetidine significantly attenuate this effect (from 71.9% to 21.6%, P<0.001 and from 71.4% to 35.9%, P=0.003, respectively). Furthermore, chlorpheniramine and cimetidine significantly decreased onset of first abdominal writhing (latency) in comparison with extract (P<0.05), however naloxone, cyproheptadine and phentolamine had no effect on antinociception and the latency induced by F. vulgare. The ED50 value for antinociceptive effects of extract was 87.6 mg/kg. These results suggest that antinociceptive effects of F. vulgare are partially mediated by histamine H1 and H2 receptors.

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