Antidepressant Effect of Baicalin Extracted from the Root of Scutellaria baicalensis. in Mice and Rats

Abstract

The flavonoid baicalin, isolated from the dried root of Scutellaria baicalensis. G. (Labiatae), is widely used in traditional Chinese herbal medicine. In the present study, baicalin, at doses of 20, 40, and 80 mg/kg (p.o.), reduced immobility time in tail suspension test (TST) and the forced swimming test (FST) in mice. Baicalin also decreased immobility time at 12.5, 25, and 50 mg/kg (p.o.) in FST in rats. Furthermore, baicalin (25 mg/kg), as well as fluoxetine (FLU; 20 mg/kg), showed a significant recovery in sucrose intake compared with the vehicle-treated stressed animals for 5 weeks treatment in a chronic mild stress (CMS) model in rats. The effect of baicalin at the dose of 25 mg was as potent as that of reference antidepressant FLU (20 mg/kg) in the CMS model. With the monoamine oxidase (MAO A and B) assay, oral administration of baicalin at the doses of 12.5, 25, and 50 mg/kg significantly inhibited MAO A activity in a dose-dependent manner in rats. However, only baicalin at the doses of 25 and 50 mg/kg markedly inhibited MAO B activity. Neither baicalin nor FLU, at the doses tested, produced a significant effect on locomotor activity in mice. These results suggest that baicalin had a specific antidepressant-like effect in vivo.. The antidepressant activity of baicalin may be mediated in part through MAO A and B inhibition in rat brain.