Evaluation of the effect of hydro-alcoholic extract of henbane seed on acute and chronic pain in male rats

The pain as the most prevalent medical problem and an unpleasant experience obliges patients to use sedatives. Recent studies have shown that anticholinergic alkaloid compounds have antinociceptive property. Regarding the presence of anticholinergic alkaloid compounds in henbane (hyoscyamus niger) and since this plant was mentioned as sedative in Iranian traditional medicine, the aim of present study was to investigate the antinociceptive effect of oral and injective administration of henbane seed on formalin-induced acute and chronic pain in rats. Male rats weighing 300-350 gr from NMRI strain were chosen randomly, and alcoholic extract of henbane seed were injected at doses of 500, 1000 and 2000 mg/kg intraperitoneally(n=10 for each dose). Also oral henbane seed at ratio of 1/14 in standard food was given to another group of rats (n=8) for 2 weeks. Acute and chronic pain scores were assessed in control (n=8) and experimental groups by formalin test. The reactions against the pain were carried out via formalin test, based on the standard criteria assessment. In addition, the antinociceptive effect of sodium salisilate as a positive control group was examined. Statistical analysis of findings showed that injection of alcoholic extract of henbane seed in all doses decreased the formalin-induced acute and chronic pain significantly (P<0.001). In addition, oral administration of henbane seed caused significant decrease of formalin-induced chronic pain (P<0.001) relative to control group. The results of the present study indicate that henbane extract has significant antinociceptive effect on both acute and chronic phases of formalin test. In addition, oral administration of henbane seed has only antinociceptive effect on formalin-induced chronic pain. It could be resulted from different mechanisms of extract injection and oral administration henbane in acute pain.