A Report on the Antidepressant-like Activity of Paullinia pinnata Methanol Leaf Extract in Mice and Possible Involvement of Monoaminergic Mechanisms

In West Africa, Paullinia pinnata (P. pinnata) alcohol leaf extracts are used to treat disorders such as depression and anxiety with no documented scientific justification. We have therefore evaluated the potential anxiolytic and antidepressant effects of Paullinia pinnata methanol leaf extract (PPME) in mice, along with probable underlying mechanisms. Adult Swiss albino mice were administered 100, 200, and 400 mg/kg of PPME orally before subjecting them through elevated plus maze (EPM) and hole-board tests to assess the anxiolytic effect. The tail suspension test (TST) and the forced swim test (FST) were used to assess the antidepressant-like effects. Reserpine, labetalol, and risperidone were used to investigate probable mechanisms of action. In both FST and TST, the duration of immobility was considerably reduced by PPME. Conversely, PPME had no significant effect on the number of mice who dipped their heads into the hole-board or entered the EPM’s open arm. Mechanistic analysis revealed that in mice given labetalol or risperidone beforehand, PPME dramatically reduced the length of immobility and reversed ptosis and akinesia caused by reserpine. Our findings suggest that PPME possesses antidepressant-like, but not anxiolytic-like, effects in mice, and antidepressant action may involve enhancing noradrenergic and serotonergic mechanisms.