Amir Larki-Harchegani - Medicinal Plants and Natural Products Research Center, Hamadan University of Medical Sciences, Hamadan, Iran- Department of Pharmacology and Toxicology, School of Pharmacy, Hamadan University of Medical Sciences, Hamadan, Iran
Abbas Ehsankia - Department of Pharmacology and Toxicology, School of Pharmacy, Hamadan University of Medical Sciences, Hamadan, Iran
Sara Ataei - Department of Biotechnology, Biological science, Alzahra University, Tehran, Iran
Fakhriosadat Hosseini - Department of Clinical Pharmacy, School of Pharmacy, Hamadan University of Medical Sciences, Hamadan, Iran
Rasool Haddadi - Medicinal Plants and Natural Products Research Center, Hamadan University of Medical Sciences, Hamadan, Iran- Department of Pharmacology and Toxicology, School of Pharmacy, Hamadan University of Medical Sciences, Hamadan, Iran

Background: Iranian traditional medicine uses hyssop (Hyssopus officinalis) as an effective medicinalplant to reduce pain and inflammation in different diseases. Although the anti-inflammatory effect ofthis plant is proved, there is no study into its analgesic effects. Thus, this study aimed to investigate theanalgesic effect of the hydroalcoholic extract from hyssop flowers and upper branches.Methods: This experimental study was conducted on ۶۶ male rats that were divided into several groupsincluding a saline control group, the groups of different doses of hyssop extract, morphine positivecontrol group, the groups of hyssop extract plus morphine, and the most effective dose of the hyssopextract plus naloxone. All injections were administered intraperitoneally, and the pain was measuredthrough the tail flick test.Results: Based on the results, ۶۰۰ mg/kg was the most effective analgesic hyssop extract dose, and themost analgesic effect was observed at ۴۵ minutes after administration. In addition, the administration ofthe most effective extract dose (۶۰۰ mg/kg) plus morphine significantly improved the analgesic effectsof morphine (P < ۰.۰۰۱). Finally, the administration of naloxone plus the most effective extract dose (۶۰۰mg/kg) significantly reduced the analgesic effect of the extract (P < ۰.۰۵).Conclusion: Overall, the hydroalcoholic extract of hyssop has analgesic effects that are probably appliedthrough opioid receptors.

Hyssop, Pain, Tail flick test, Rat