Anxiolytic-like Effects of Methanol Extract of Zizyphi Spinosi Semen in Mice

Zizyphi Spinosi Semen (ZSS), a traditional Chinese folk medicine, has been used for treatment of insomnia and anxiety. This experiment was performed to investigate the anxiolytic-like effect of methanol extract of ZSS (MEZSS) in mice by using the experimental paradigms of anxiety and compared with that of a known anxiolytic, diazepam. In the elevated plus-maze test, it showed that MEZSS (100 mg/kg, p.o.) and diazepam (2.0 mg/kg, p.o.) increased the percentage of time spent on the open arms and the number of open arms entries. MEZSS (50, 100 and 200 mg/kg, p.o.) and diazepam (0.5 mg/kg, p.o.) significantly increased the number of head dips compared with that of control group in the hole-board test. However, MEZSS has no effect on decreasing the locomotor activity, while diazepam (2.0 mg/kg, p.o.) significantly inhibited locomotor activity. MEZSS did not decrease the strength force in the grip strength test, either. In addition, GABAergic involvements were also investigated to understand the possible mechanisms. $GABA_{A}$ receptors subunits and glutamic acid decarboxylase (GAD) were not over expressed, compared with that of the saline group. We also found that MEZSS did not increase chloride influx in cultured cerebellar granule cells. It is concluded that MEZSS might have anxiolytic-like effects, but these effects might not be mediated by GABAergic transmission.