Journal of Ethnopharmacology 103 (2006) 345–349 Evaluation of the analgesic effect of Echium amoenum Fisch & C.A. Mey. extract in mice: Possible mechanism involved Mahmoud Reza Heidari a,∗ , Elham Moein Azad a , Mitra Mehrabani b a Department of Toxicology and Pharmacology, Faculty of Pharmacy and Neuroscience Research Center and Physiology Research Center, Kerman University of Medical Sciences, Kerman, P.O. Box 76175-493, Iran b Department of Pharmacognosy, Faculty of Pharmacy, Kerman, Iran Received 1 October 2004; received in revised form 26 July 2005; accepted 11 August 2005 Available online 26 September 2005 Abstract Echium amoenum Fisch & C.A. Mey. has been used in Iranian traditional medicine as demulcent and analgesic in common cold from long ago. In this investigation, the analgesic effect of the methanolic extract of the petals of this plant on male albino mice was evaluated by formalin and hot-plate test. The methanolic percolated extract with different doses 5, 10, 20 and 30 mg/kg were injected intraperitoneally to mice. The results showed that the dose of 10 mg/kg of extract had the highest analgesia in formalin (P < 0.05) and hot-plate test (P < 0.01) compared to the control group. The analgesic effect of extract was lower than morphine 2.5 mg/kg and ASA 300 mg/kg in the chronic phase of pain in formalin test (P < 0.05) and in hot-plate test too (P < 0.05). Pretreatment of animal with naloxone 4 mg/kg, s.c. 5 min before extract, decreased the analgesia induced by extract in hot-plate and acute phase of formalin tests; therefore, the opioid receptor may be involved at least partly in the analgesic effect of Echium amoenum extract. The results suggested that Echium amoenum extract has a suitable analgesic effect and further studies are required to evaluate these effects and the potential of the plant. © 2005 Elsevier Ireland Ltd. All rights reserved. Keywords: Echium amoenum; Pain measurement; Formalin test; Hot-plate test 1. Introduction In analysis the research during the last decades, it is estimated that the analgesics are one of the highest therapeutic categories on which research efforts are concentrated (Elisabetsky and Castilhos, 1990). Analgesic compounds available in the mar- ket, still present a wide range of undesired effects (Katzung, 2001) leaving an open door for new and better compounds. Natural products are believed to be an important source of new chemical substance with potential therapeutic applicabil- ity. Several plant species traditionally used as analgesics (Mills and Bone, 2000). There are reports about analgesic effects of medicinal plants in the literatures (Cakci et al., 1997; Garrido et al., 2001; Hajhashemi et al., 2002; Khanna and Bhatia, 2003; Mandegary et al., 2004; Monsef et al., 2004; Vian et al., 2003). ∗ Corresponding author. Tel.: +98 341 3220001 3; fax: +98 341 3220799. E-mail addresses: heidarimr@yahoo.com, mrheidari@kmu.ac.ir (M.R. Heidari). Echium amoenum Fisch & C.A. Mey. (Boraginaceae) is one of the important medicinal plants in Iranian traditional medicine (Hooper, 1937; Zargari, 1996). Petals of Echium amoenum have been advocated for variety of effects such as demulcent, anti-inflammatory and analgesic, especially for common cold, anxiolytic and sedative in folk medicine of Iran (Amin, 1991; Hooper, 1937; Shafaghi et al., 2002; Zargari, 1996). On the basis of the above facts and our interest for analgesic drugs, this inves- tigation was performed. Echium amoenum is a biennial or perennial herb indigenous to the narrow zone of northern part of Iran and Caucasus, where it grows at an altitude ranging from 60 to 2200 m (Rechinger, 1967). Four species of Echium are available in Iran (Mozaffarian, 1996). There are some reports about anxiolytic effects of Echium amoenum (Rabbani et al., 2004; Shafaghi et al., 2002) and another that it has the capacity of increasing the cellular immune response (Amirghofran et al., 2000). The present work was carried out to investigative the anal- gesic activity of methanolic extract of Echium amoenum by chemical method, formalin test (Hunskaar and Hole, 1987; 0378-8741/$ – see front matter © 2005 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.jep.2005.08.027