Pharmacological studies on the anxiolytic effect of standardized Schisandra lignans extract on restraint-stressed mice

Fruits of Fructus Schisandrae were used as sedatives and hypnotics in traditional Chinese medicine for a long history. In this study, we investigated the effects of schisandra lignans extract (SLE) on anxiety disorder in restraint-stressed mice using light-dark (L-D) test. The influences of restraint stress on the levels of monoamines: noradrenaline (NE), dopamine (DA) and serotonin (5-HT) in cerebral cortex, as well as plasma corticosterone (CORT) were studied in mice. The HPLC fingerprint of SLE was recorded and the percentage composition of Schisandra lignans was determined as 82.63%. In L-D test, it was found out that 18 h of restraint stress significantly decreased the anxiolytic parameters (explorative behaviors, e.g. number of entries, time spent) in light area indicating high state of anxiety in stressed mice. In addition, restraint stress elevated NE, DA, and 5-HT levels in cerebral cortex of anxiety mice. Plasma CORT level was also increased. Oral administration of SLE (100 and 200 mg/kg/day, 8 days) emolliating the level of stress-induced anxiety by significantly increasing the anxiolytic parameters mentioned above. We also observed decreases in cerebral cortex monoamines levels, as well as plasma CORT level in stressed mice. These results suggested that SLE reversed stress-induced anxiety level, changes of cortex monoamine transmitters and plasma CORT. The anxiolytic effects of SLE might be related to its anti-stress activity by modulation of hyperactive HPA axis.