The involvement of magnoflorine in the sedative and anxiolytic effects of Sinomeni Caulis et Rhizoma in mice

The present study seeks to evaluate the sedative and anxiolytic effects of the 70 % ethanol extract of Sinomeni Caulis et Rhizoma (SR). The extract was orally administered to mice at dosages of 25, 50, 100, 200 or 400 mg/kg. The mice were then subjected to an array of behavioral tests to assess the sedative (open-field, rota-rod, and thiopental sodium-induced sleeping test) and anxiolytic (elevated plus maze test) effects of the substance. SR (100, 200 mg/kg) significantly reduced locomotor activity, decreased rota-rod performance, and potentiated thiopental sodium-induced sleeping in mice, all indicative of its sedative effects. SR (50, 100 mg/kg) also produced anxiolytic effects, as shown by an increase in entries and staying time on the open arm of the plus maze. SR’s sedative and anxiolytic effects were comparable to that of the benzodiazepine, diazepam. Moreover, to identify SR’s probable mechanism of action, intracellular Cl⁻ ion influx was observed in cultured human neuroblastoma cells. SR dose-dependently increased Cl⁻ influx, which was blocked by co-administration of the GABA_A receptor competitive antagonist, bicuculline. Among the major constituents of SR, only magnoflorine showed a similar increment in Cl⁻ influx, which was also blocked by bicuculline. Altogether, the present results suggest that SR has sedative and anxiolytic effects, probably mediated by magnoflorine through a GABAergic mechanism of action.