Antidepressant effect of Melissa officinalis in the forced swimming test

Background: In Iranian and other traditional medicines, an antidepressant effect has been indicated for Melissa officinalis (Lamiaceae). However, studies showing its antidepressant effect is lacking. Therefore, the present study was undertaken to examine whether the aqueous extract and essential oil from leaves of Melissa officinalis have an antidepressantlike activity in mice. Materials and Methods: The effect of subchronic administration of different doses of the aqueous extract (25,75, 150, 300 mg/kg or water; n=9-10) and the essential oil (10, 25, 75, 150,300 mg/kg or almond oil; n=9-10) on immobility, climbing, and swimming behaviors were evaluated in the forced swimming test. Fluoxetine (20mg/kg) and imipramine (15 mg/kg) were used as reference drugs. Additionally, the effect of both plant preparations on spontaneous activity was examined. Results: All doses of the aqueous extract, used in this study, produced a significant reduction in immobility along with an increase in climbing behavior which is similar to those which have been observed with imipramine. Essential oil caused a dose-dependent reduction in immobility and an increase in climbing at all studied doses, compared to control group. Only the highest dose (300mg/kg) of essential oil showed a significant increase in swimming behavior. The aqueous extract, but not the essential oil, decreased spontaneous activity in a dose dependent manner. Conclusion: The results of this study suggests that the Melissa officinalis possess an antidepressant-like activity similar to imipramine which may have a potential clinical value for treatment of depression.