Antidepressant-like effects of flavonoids extracted from Apocynum venetum leaves in mice: the involvement of monoaminergic system in mice

The present study investigated a possible antidepressant-like activity of flavonoids extracted from Apocynum venetum leaves using two predictive tests for antidepressant effect on rodents: the forced swimming test (FST) and the tail suspension test (TST). Additionally, the monoaminergic mechanisms involved in the antidepressant-like effect of AV-extract in the mouse forced swimming test (FST) were evaluated. The extract (25, 50 and 100 mg/kg, i.g.) produced antidepressant-like effects in the FST and TST, without accompanying changes in ambulation distances (open-eld test). The antidepressant-like effects of AV-extract (50 mg/kg, i.g.) was prevented by the pretreatment of mice with ketanserin (5 mg/kg, s.c., a serotonin 5-HT2A receptor antagonist), cyproheptadine (3 mg/kg, i.g., a serotonin 5-HT2 receptor antagonist), prazosin (1 mg/kg, i.g., an α1-adrenoceptor antagonist), yohimbine (1 mg/kg, i.g., an α2-adrenoceptor antagonist) or propranolol (2 mg/kg, i.g., aβ-adrenoceptor antagonist), SCH23390 (0.05 mg/kg, i.g., a dopamine D1 receptor antagonist) and sulpiride (50 mg/kg, i.g., a dopamine D2 receptor antagonist). By contrast, pretreatment of mice with WAY 100635 (0.1 mg/kg, s.c., a serotonin 5-HT1A receptor antagonist) did not counteract the antidepressant-like effect of AV-extract in the TST. It can be concluded that the AV-extract produces an antidepressant-like effects in the FST and in the TST through interaction with the serotonergic (5-HT2A and 5-HT2 receptors), noradrenergic (α1-adrenoceptor, α2-adrenoceptor, a β-adrenoceptor) and dopaminergic (D1 and D2 receptors) systems. Taken together, our results suggest that AV-extract deserves further investigation as a putative alternative therapeutic tool that could help the conventional pharmacotherapy of depression.   Key words: Antidepressant, AV-extract, serotonergic, noradrenergic, dopaminergic, tail suspension test, forced swimming test.