RESUMO
Previous work has shown that intraperitoneal administration of riparin III (ripIII) reduces immobility time in the forced swimming test (FST), which suggests potential antidepressant activity. As the mechanism of action is not completely understood, this study is aimed at investigating the antidepressant-like action of ripIII. Following intraperitoneal administration of ripIII at doses of 25 and 50 mg/kg, there were decreases in the immobility time in the FST and tail suspension test without accompanying changes in ambulation (data not shown). The pretreatment of mice with sulpiride (50 mg/kg, i.p.), prazosin (1 mg/kg, i.p.), yohimbine (1 mg/kg, i.p.), and p-chlorophenylalanine (PCPA, 100 mg/kg, i.p. for, four consecutive days) significantly prevented the anti-immobility effect of ripIII in the FST. On the other hand, the anti-immobility effect of ripIII (50 mg/kg, v.o.) was not altered by pretreatment of mice with SCH23390 (15 µg/kg, i.p.) Furthermore, ripIII potentiated the sleeping latency and sleeping time of the pentobarbital-induced sleeping time test and also potentiated apomorphine (16 mg/kg, i.p.)-induced hypothermia in mice. In conclusion, the present study provides evidence that the antidepressant-like effect of ripIII is dependent on its interaction with the serotonergic, noradrenergic (α1- and α2- receptors), and dopaminergic (dopamine D2 receptors) systems.