Background and purpose: Ferula szowitsiana is one of the Iranian medicinal plants that could be effective for pain relief since it affects opioid, cannabinoid and adenosine receptors. In this study the effects of hydroalcoholic extract of Ferula szowitsiana on pain was investigated in rats.

Materials and methods: Hydroalcoholic extract of Ferula szowitsiana was solved in saline, ethanol and tween 80 (8:1:1). Male rats weighing 200-250g were placed in different groups: control, control with visceral pain, intraperitoneal administration (i.p.) of solvent, solvent with visceral pain, doses of 50, 100, 200, and 400 mg/kg of extract, naloxone, extract with naloxone, extract with visceral pain, intrathecal administration (i.t.) of solvent, 8μg/10μl of extract and 8μg/10μl of extract with visceral pain groups. Tail flick apparatus were used for thermal pain assessment.

Results: Ferula szowitsiana extract reduced thermal pain threshold (P<0.01). The i.t administration of equivalent concentration of effective dose of extract which was used in i.p administration did not lead to a significant hyperalgesia unlike the systemic administration. On the other hand, the results showed no significant difference between the group receiving the extract and extract-naloxone groups. Also i.p. administration of extract caused a visceral pain (P<0.001).

Conclusion: Ferula szowitsiana extract leads to visceral pain in i.p. administration and referred pain in tail region, therefore, it causes the activation of TRPV1 receptors in indirect pathway and then reduce thermal pain threshold.