Anxiolytic effects of Lippia citriodora in a mouce model of anxiety

Lippia citriodora is commonly used in Iranian folk medicine for treatment of many disorders. Since there scientific data to prove the anxiolytic properties of this plant in Iran are scarce, we aimed to evaluate the sedative and anxiolytic activity of the leaf extract and essence of L. citriodora in an animal model of anxiety. The extract and the essence used were obtained after maceration and hydro-distillation of the leaves of L. citriodora, respectively. We evaluated the anti-anxiety profile and sedative activity of diazepam (1 mg/kg i.p. as the standard), hydroethanolic extract (200 and 400 mg/kg i.p.) and the essence (10, 15, and 50 mg/kg i.p.) of leaves of L. citriodora using elevated plus-maze and locomotor activity. We also used flumazenil, to find out if the possible effects are mediated through gamma-aminobutyric acid (GABA)/benzodiazepine receptor complex. The results showed that the essence of L. citriodora at a dose of 15 mg/kg is the most effective anxiolytic dose. Interestingly, flumazenil reversed this action of the essence as well as that of diazepam. The extract even at a dose of 400 mg/kg did not show significant anxiolytic effect. In locomotor activity studies, the essence caused sedation to a lesser extent than diazepam. The results suggest that the essence of this plant could be a better candidate for further analysis and fractionation. As the anxiolytic effect of the essence is reversed by flumazenil, it is possible that the GABA receptor could be involved in mediating these effects.