Antinociceptive activity of Ricinus communis seed's hydroethanolic extract on male Balb/C mice

Pain is a normal protective response to tissue injury caused by physical trauma, noxious chemicals and microbiological agents. Use of chemical drugs and medicinal plants is a conventional method to manage pain; however, their side effects have caused increased tendency to the use of herbal medicines among patients. This study was conducted to investigate antinociceptive action of Ricinus communis seed's extract (RCE) in male Balb/C mice. In this experimental study, 72 male mice weighing 25-35gr were used. Animals were randomly divided into six groups of 12 mice each, including: Control group, three groups separately treated respectively with 100, 200, and 400mg/kg hydroethanolic R. communis seed extract, morphine (1mg/kg)-treated group, and naloxone (0.1mg/kg) + R. communis seed extract (200mg/kg)-treated group. All animals received extract and drugs intraperitoneally. To evaluate the analgesic effect of the extract, writhing and tail flick tests were used. The 200 and 400mg/kg of the extract significantly increased pain threshold compared to the control group in writhing and tail flick tests (P < 0.01). Moreover, 400mg/kg of the extract showed a stronger antinociceptive effect especially in writhing test compared to the control and other treated groups (P < 0.001). Analgesic effects of hydroethanolic R. communis seed extract observed in the tail flick and writhing tests are probably related to activation of opioid system. Results may suggest that this plant extract might be beneficial in relieving human pain