Biol. Pharm. Bull. 30(9) 1748—1753 (2007)

population. Current pharmacological approaches focus primarily on the g-aminobutyric acid (GABA)-ergic system, the major inhibitory neurotransmitter system of the central nervous system (CNS). Drugs that enhance synaptic GABA-ergic neurotransmission are widely utilized in the clinical setting for their sedative or hypnotic effects. Several classes of compounds—GABA, benzodiazepines, barbiturates, steroids and alcohol—act at different sites of the GABA/benzodiazepine receptors-chloride channel complex to increase the opening of the channel. In this way, they increase chloride currents through the GABAA receptors and enhance inhibitory synaptic transmission. GABAA receptors have been known to play an important role in the modulation of barbiturate-induced sleeping through the interaction with GABA-ergic system. Zizyphi Spinosi Semen (ZSS), the dried seed of Zizyphus jujuba MILL var. spinosa (Rhamnaceae), has been used as a tranquilizer, an analgesic and an anticonvulsant in oriental countries such as China, Japan and Korea for centuries, and also has been prescribed for the treatment of insomnia and anxiety in Asia. In modern pharmacological studies, ZSS is known to contain many pharmacologically active components such as alkaloids, triterpenes and flavones. These compounds have been shown to have central inhibitory activity. Cyclopeptide alkaloids from ZSS were demonstrated to be the major hypnotic components of ZSS. Therefore, we were interested to investigate whether sanjoinine A (Fig. 1), one of major alkaloid compounds, exerts hypnotic effect and/or enhances pentobarbital-induced sleeping behaviors through GABA-ergic systems. MATERIALS AND METHODS