This experiment was performed to investigate whether methanol-extract of Zizyphi Spinosi Semen (MEZSS) has hypnotic effects and/or enhances pentobarbital-induced sleep behaviors through the γ-aminobutyric acid (GABA)-ergic systems.MEZSS significantly inhibited the locomotion activity in mice.MEZSS enhanced pentobarbital-induced sleep and reduced the onset of sleep time.However, MEZSS itself did not induce sleep at higher dose in this experiment.In addition, both of MEZSS and pentobarbital increased chloride influx in primary cultured cerebellar granule cells.MEZSS significantly increased GABAA receptors γ-subunit expression, and slightly decreased β-subunit expression, and had no effect on the expression of α-subunits in hypothalamus and thalamus in mice, showing more similar subunit expression from diazepam than pentobarbital.In addition, MEZSS also enhanced expression of glutamic acid decarboxylase (GAD), but pentobarbital and diazepam did not.In conclusion, MEZSS itself does not induce sleep, but it augments pentobarbital-induced sleep behaviors through the modification of GABAergic systems.