Involvement of l-arginine-nitric oxide pathway in the antidepressant and memory promoting effects of morin in mice.

l-Arginine-nitric oxide pathway has been reported to be involved in the mediation of the psychopharmacological effects of many psychotropic drugs. Previous studies have shown that morin, a psychotropic compound isolated from mulberry leaf produces functional psychopharmacological effects indicative of antidepressant, antipsychotic, anxiolytic and nootropic properties. However, the role of l-arginine-nitric oxide pathway in the psychotropic effects of morin has not been fully investigated, hence, the need for this study. Male Swiss mice were pretreated individually or in combination with nitric oxide precursor [l-arginine (750 mg/kg, i.p.)], competitive nonselective nitric oxide synthase (NOS) inhibitor [N(G)-nitro-l-arginine methyl ester (l-NAME, i.p) (50 mg/kg)] or selective neuronal NOS inhibitor [methylene blue (3.75 mg/kg, i.p)] prior to morin (100 mg/kg, i.p.) or saline (10 mL/kg, i.p.) treatment. Psychopharmacological activities were then evaluated 30 min later using open field, Y-maze, and forced swim tests. l-Arginine significantly reversed the effects of morin on locomotion, memory and depression in mice. The reduced motor activity and enhanced memory function produced by morin were significantly attenuated by methylene blue but augmented the antimobility activity of morin in the FST. Moreover, l-NAME potentiated the psychopharmacological effects of morin in the open field and forced swim tests but reduced its memory promoting effect. Meanwhile, morin supplementation reversed the effects of l-arginine on l-NAME-treated mice in all behavioral models. The results of this study suggest that l-arginine-nitric oxide pathway might play a role in the modulation of the antidepressant and memory promoting effects of morin in mice.