RESUMO
Depression has become of universal major importance, and it is therefore vital to expand the armamentarium for treating the condition. Lack of motivation and lassitude are major symptoms treated with the use of Marapuama (Ptychopetalum olacoides, PO) remedies by communities in the Brazilian Amazon. Considering the prominence of such symptoms in depression, the present study was designed to verify the effects of a standardized PO ethanol extract (POEE) on the forced swimming (FST) and tail suspension tests (TST). POEE i.p. (15-100 mg/kg) and oral (300 mg/kg) resulted in a significant and dose-related anti-immobility effect. We further examined the involvement of dopamine, noradrenaline and serotonin in these antidepressant-like effects. POEE effects were prevented when catecholamine synthesis was inhibited by -alpha-methyl-rho-tyrosine (AMPT) (100 mg/kg, i.p.), while inhibition of serotonin synthesis with rho-chlorophenylalanine methyl ester hydrochloride (PCPA) (100 mg/kg, i.p.) was devoid of effect. The blockade of beta-adrenergic (propranolol 2 mg/kg, i.p.) and D(1) dopamine (SCH 23390 0.5 mg/kg, i.p.) receptors prevented POEE anti-immobility effects; by contrast, blockade of D(2) dopamine (sulpiride 2 and 50 mg/kg, i.p.) receptors was ineffective. Consistent with traditional use, the results indicate that POEE possesses antidepressant-like effects, possibly mediated by beta-adrenergic and D(1) dopamine receptors.