Evaluation of the analgesic effect of Echium amoenum Fisch & C.A. Mey. extract in mice: possible mechanism involved.

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.