The ethanol extract of Cirsium japonicum increased chloride ion influx through stimulating GABA(A) receptor in human neuroblastoma cells and exhibited anxiolytic-like effects in mice.

The aim of the present study was to evaluate the anxiolytic effects of the ethanol extract of Cirsium japonicum (CJ) in mice. The extract was orally administered at dosages of 50, 100, 200, or 400 mg/kg of body weight. The CJ-induced behavioral changes were assessed using the open-field and elevated-plus maze test. The ethanol extract of CJ did not affect overall locomotor activity of mice in the open-field test, however, it showed increase exploration in the unprotected center zone, which is thought to reflect anxiolyticlike effects. Furthermore, the CJ extract (100 and 200 mg/kg) significantly increased the percentage of time spent in the open arms of the elevated plus-maze, indicating the anxiolytic effects of the substance. This anxiolytic effects of the extract were comparable to that of the benzodiazepine, diazepam. To further characterize the anxiolytic activities of CJ, its action on human neuroblastoma cells were assessed. The CJ extract dose-dependently increased chloride ion (Cl(‒)) influx, which was blocked by coadministration of the GABA(A) receptor competitive antagonist, bicuculline, suggesting a GABA(A) receptor - Cl(‒)) channel mechanism of action. Taken altogether, the present study demonstrates that the ethanol extract of CJ has anxiolytic effects, probably mediated through GABAergic neurotransmission.