Evaluation of the analgesic effect of aqueous extract of Elaeagnus angustifolia in writhing test: possible mechanism effect

Majid Motaghinejad, Manijeh Motevalian, Ozra Motaghinejad. Department of pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran

Objective: Elaeagnus angustifolia is a traditional herbal medicine widely used as an anti-inflammatory, sedative, spasmolytic and anti- allergic agent. This plant has been used In Iranian folkloric medicine for colic and other digestive diseases. In this study anti nociceptive mechanisms of Elaeagnus angustifolia were examined in writhing test as a model of visceral pain. For evaluation of the anti-nociceptive mechanisms of Elaeagnus angustifolia, we examined the effect of dopaminergic, adrenergic , serotonergic, histaminergic and opioid receptor antagonists on analgesic effects of aqueous extract of Elaeagnus angustifolia in rats.

Materials & Methods: Eighty eight male adult mice 25-30 grams (mean weight 27.5± 0.2grams) were randomly divided to 11 groups. Group(I, II): negative & positive control groups, received normal saline and indomethacin (5mg/kg) respectively. Groups (III, IV, V): were injected with 250, 500 and 700 mg/kg of aqueous extract of Elaeagnus angustifolia. Groups(VI, VII, VIII, IX, X, XI): were pretreated with either Dopaminergic receptor antagonist (metocloperamide, 2mg/kg), adrenergic receptor antagonist (phentolamine, 20mg/kg),serotonin receptor antagonist (cyproheptadine, 4mg/kg), opioid receptor antagonist (naloxone, 2mg/kg), Histamine type 2 receptor antagonist (cimetidine, 10mg/kg) and type 1 receptor antagonist (chlorpheniramine, 10mg/kg) then all groups received single dose of Elaeagnus angustifolia aqueous extract (700mg/kg). All injections were performed intraperitonealy (ip). All animals were injected with acetic acid 0.8% (10ml/kg) for visceral pain induction, 30 minutes after treatments. Antinociceptive activity was expressed as percentage inhibition of abdominal constriction.

Results & Conclusion: The result of this study showed that aqueous extract of Elaeagnus angustifolia at doses of 250mg/kg, 500mg/kg and 700mg/kg caused a statistically significant reduction in the number of acetic acid- induced writhing in mice compared to control groups, with P < 0.05 (ANOVA). These effects were also dose- dependent and comparable to the analgesic effects obtained with morphine which was used as a reference drug. The percentage inhibition of writhing response exhibited by extracts of 250, 500 and 700mg/kg were 20%, 24% and 37% respectively. Indometacine inhibited the writhing response by 74%. Also in treatment groups, our study showed that groups VI, VIII, X, XI did not show significant changes in response compared to the group V which had no antagonist treatment and groups VII and IX showed a significant reduction in response compared to group V with p<0.05 (Student’s T-test). The responses in group V in presence of antagonists were reduced by 15% and 18% respectively. According to the data obtained, it seems that the aqueous extract of Elaeagnus angustifolia is potentially benefitial in inhibition of visceral pain. Also we conclude that opioid and adrenergic system have important role in mechanism of this inhibition. Also according to our finding, we can assume that serotonergic, histaminergic (H1 & H2) and dopaminergic system are not involved in this process.

Key word: Elaeagnus angustifolia, writhing test , visceral pain, histamine, Dopamine, serotonin