Anxiolytic and Antidepressant Effects of Aqueous Extract of Stachys lavandulifolia Vahl. in Mice

Background: Stachys lavandulifolia Vahl. is a widely used plant in Iranian traditional medicine. It has long been used as an anxiolytic herb. The aim of this work was to investigate the anxiolytic and antidepressant properties of aqueous extract of aerial parts of Stachys lavandulifolia Vahl. in mice. 
Materials and Methods: For evaluation of anxiolytic and antidepressant effects of the plant, different doses (500, 1000, 1200, and 1400 mg/kg) of the extract were used in the mouse models of elevated plus maze (EPM) and forced swimming test (FST), respectively. The possible anxiolytic mechanism of the extract was determined by using pentylenetetrazol (PTZ) (10 mg/kg), propranolol (0.2 mg/kg), and atropine (0.5 mg/ kg). Sedative effect of the extract was evaluated by ketamine sleeping time test, and rotarod was used to determine the effects of the extract on motor function. Statistical analysis was performed using one-way analysis of variance (ANOVA). 
Results: The results showed that the percentage of time spent and number of entries is significantly increased (P < 0.05) with doses of 1000 and 1200 mg/kg of the extract. PTZ but not propranolol or atropine reversed the effects of the extract (1000 mg/kg) on EPM. Neither doses of the extract could decrease the immobility of the mice in FST (P >0.05). Motor coordination was impaired (all doses) by the plant. 
Conclusion: This study confirms the anxiolytic properties of aqueous extract of S. lavandulifolia and suggests that its effects are mediated through GABAA receptors. The extract does not have sedative properties but the results are indicative of a coordination impairing potential of the extract.