Introduction: Previous studies have revealed analgesic, anti-inflammatory, and antioxidant properties of Mentha piperita (MP). Hence, in this study, the antidepressant effects of the ethanolic extract of MP in forced swim test (FST) and tail suspension test (TST) in male mice were investigated.
 
Materials & Methods: In this experimental study, 96 male mice were randomly divided into 12 groups of 8 that received normal saline (10 ml/kg), imipramine (30 mg/kg), fluoxetine (20 mg/kg), and different doses of MP (100, 200 and 400 mg/kg), respectively. In FST, immobility time, swimming time, and climbing time and immobility time in TST were recorded during 6 minutes. In this study, all the drugs and extracts were injected intraperitoneally (i.p.) at the constant volume of 10 ml/kg.
 
Findings: Results shows that 200 and 400 mg/kg of the extract, as well as fluoxetine and imipramine reduced immobility time compared to the control group in FST and TST (p<0.001). In addition, the ethanolic extract and fluoxetine increased swimming time (p<0.001) without any significant change in climbing time (p>0.05). In contrast, imipramine increased climbing time without any significant change in swimming time (p>0.05).
 
Discussion & Conclusions: This extract like serotonergic agents (e.g., fluoxetine) decreases immobility time and increases swimming time without any significant change in climbing time. Hence, MP compounds (especially menthol) induced their effects through serotonergic mechanism. However, further studies are needed to clarify their exact mechanism of action.