Efeito antidepressivo da riparina II : investigação do mecanismo de ação através das alterações comportamentais, neuroquímicas e do estresse oxidativo

Abstract

Depression is a disabling and recurrent disease whose clinical treatment is related to modulations in monoaminergic systems in various brain areas. Riparina II (ripII), alkamide isolated from unripe fruit of Aniba riparia, has shown previously antidepressant-like effects in animal behavioral models. Thus, in order to investigate the potential antidepressant ripII, behavioral experiments were performed as the forced swim, tail suspension and open field tests. To assess the involvement of monoaminergic system, animals were pretreated with specific antagonists to 5-HT1A-, 5-HT2A/2C-, and 5-HT3-serotonin (5-HT) receptors, to D1- and D2-dopamine (DA) receptors and to 1- and 2-noradrenaline (NA) receptors in the forced swimming test. Furthermore, animals pretreated with ripII and submitted to the forced swim test had their brain areas such as hippocampus, striatum and prefrontal cortex removed for detection of monoamine levels in HPLC electrochemical or to carry out the experiments of oxidative stress. In the oxidative stress assays we investigated enzymatic activities of superoxide dismutase, measured the levels of reduced glutathione (GSH) and nitrite/nitrate, and lipid peroxidation degree. RipII was acutely administered orally at a dose of 50 mg/kg in all tests. The results showed that ripII presented antidepressant effect on the forced swim and tail suspension tests suggesting that this effect is specific, since the animals showed no changes in locomotor activity in open field test. In the evaluation of monoaminergic systems, the results showed that the antagonists SCH23390 (D1), sulpiride (D2), prazosin (1), NAN-190 (5-HT1A) and ondansentron (5-HT3) reversed the immobility time of ripII on the forced swim test suggesting the involvement of these receptors for the antidepressant effect of ripII, while no change of this effect in the presence of the antagonists yohimbine (2) and ritanserin (5-HT2A/2C) was observed, suggesting non-participation of these receptors on the drug effect. The prior administration of ripII before the forced swimming, reversed the increased levels of lipid peroxidation and increased levels of GSH in hippocampus, striatum and prefrontal cortex. In conclusion, the study suggests a modulating action exerted by ripII on the functioning of the noradrenergic, dopaminergic and serotonergic levels in the brain, as a mechanism for the antidepressant effect in the forced swimming test, as well as the participation of direct or indirect antioxidant properties of this drug through the ability to modify the neuronal response to oxidative stress.