Involvement of the monoaminergic system in the antidepressant-like effect of the crude extract of Mentha piperita (Lamiaceae) in the forced swimming test in mice

The aim of the present study was to investigate the involvement of the monoaminergic system in antidepressant-like effects of a characterized ethanolic extract of Mentha piperita (MP) in the forced swimming test (FST) in male mice. The animals were intraperitoneally (i.p.) treated with the MP extract (50-400 mg/kg) one hour before FST. To examine the involvement of the monoaminergic system in the antidepressant-like effect of MP, receptor antagonists were administrated fifteen minutes prior to the MP extract treatment (400 mg/kg, i.p) to mice and after one hour the FST was carried out. The MP extract (200 and 400 mg/kg, i.p.) showed a significant antidepressant-like effect (P < 0.001), in the FST, but it did not change the spontaneous locomotor activities in the open-field test. Pretreatment of animals with SCH23390, sulpiride, haloperidol, prazosin, yohimbine, WAY100135, ketanserin, and p-chlorophenylalanine (pCPA) reversed the antidepressant-like effect of the MP extract (400 mg/kg, i.p.) in the FST. In addition, the administration of reserpine increased the duration of immobility elicited by the MP extract in animals. Combinations of the MP extract (50 mg/kg, i.p.,) with sub-effective doses of fluoxetine (5 mg/kg, i.p.) or imipramine (5 mg/kg, i.p.) potentiated the antidepressant-like response. The ethanolic extract of MP exerts antidepressant-like effects, which might be mediated through dopaminergic (D1 and D2), noradrenergic (α1 and α2), and serotonergic (5-HT1A, 5-HT2A) receptors. These first results including the potentiating effect of the MP extract on fluoxetine and imipramine suggest further investigations of MP for the management of depression.

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