Involvement of Opioidergic and Serotoninergic systems in the anti-nociceptive effect of Tanacetum parthenium

Introduction: Feverfew (Tanacetum parthenium) (T.p.) is widely used in folk medicine to treat many diseases. We have reported the analgesic effect of T.p. flowers and leaves previously. The present study was designed to find the mechanisms underlying the anti-nociceptive effect of the aqueous extract of T.p. flower. Methods: Based on our previous study, the dose of 50 mg/kg i.p. of the T.p. aqueous extract has a potent analgesic effect on mice (NMRI) (20 +/- 2 g) in formalin test. The same dose was used in the present study. Here, we studied the roles of opioidergic, serotoninergic and alpha-adrenergic systems in the anti-nociceptive effect of the T.p. extract. 15 min before the administration of the extract, animals were pretreated with drugs, including opioid antagonist naloxane (5mg/kg, i.p.), serotoninergic antagonist cyproheptadine (4 mg/kg, i.p.) and alpha-adrenergic antagonist phentolamine (20 mg/kg, i.p.) separately (n >= 6 in each group). Saline and the T.p. extract were used as controls. Results: Pretreatment with naloxane increased the pain sensation in the neurogenic phase of formalin test compared to the control (p<0.001). Pretreatment with cyproheptadine increased the sensation of pain in both early and late phases (p<0.05). Inhibition of alpha-adrenergic system was not able to attenuate the anti-nociceptive effect of the extract. Conclusion: These results propose the involvement of sertoninergic and opioidergic systems in the anti-nociceptive effect of the T.p. extract.