The antidepressant-like effect of a supercritical CO2 (SCCO2) Valeriana glechomifolia extract enriched in valepotriates was investigated in a mice tail suspension test (TST) and forced swimming test (FST). The SCCO2 extract decreased mice immobility in the FST (0.5-20 mg/kg p.o.) and elicited a biphasic dose-response relationship in the TST (1-20 mg/kg p.o.) with no alterations in locomotor activity and motor coordination (assessed in the open-field and rota-rod tests, respectively). The anti-immobility effect of the SCCO2 extract (5 mg/kg, p.o.) was prevented by mice pre-treatment with yohimbine (1 mg/kg, i.p., an α2 adrenoceptor antagonist), SCH 23390 (15 μg/kg, s.c., D1 dopamine receptor antagonist) and sulpiride (50 mg/kg, i.p., D2 dopamine receptor antagonist). However, mice pre-treatments with prazosin (1 mg/kg, i.p., α1 adrenoceptor antagonist) and p-chlorophenilalanine methyl ester (4×100 mg/kg/day, i.p., a serotonin synthesis inhibitor) were not able to block the anti-immobility effect of the SCCO2 extract. Administration (p.o.) of the SCCO2 extract (0.25 mg/kg) and imipramine (10 mg/kg), desipramine (5 mg/kg) and bupropion (3 mg/kg) at sub-effective doses significantly reduced mice immobility time in the FST. These data provide the first evidence of the antidepressant-like activity of V. glechomifolia valepotriates, which is due to an interaction with dopaminergic and noradrenergic neurotransmission.
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