Antidepressant-like effects and memory enhancement of a herbal formula in mice exposed to chronic mild stress

Shen Yuan Gan（SYG） is a Chinese herbal prescription composed of total saponins of Panax ginseng and total oligosaccharide esters of Polygala tenuifolia（2：1）.Our previous studies have demonstrated that SYG has antidepressant-like effects in various mouse models of behavioral depression.The present study aimed to test whether SYG affected chronic mild stress（CMS）-induced depression and cognitive impairment in mice.We found that a 5-week CMS schedule induced significant degradation of the coat state,decreased sucrose intake in the sucrose-preference test,and increased the latency to feed in the noveltysuppressed feeding test.All of these CMS-induced changes were ameliorated by SYG（100 and 200 mg/kg） and fluoxetine（10 mg/kg）.In addition,SYG restored the decreased monoamine neurotransmitter concentrations（serotonin,dopamine,norepinephrine and acetylcholine） induced by CMS in the prefrontal cortex.Interestingly,SYG ameliorated CMS-induced cognitive impairment in the step-through test,and increased the acetylcholine level in the prefrontal cortex.These results suggest that SYG has an antidepressant-like action and enhances cognition by modulating the serotonin,dopamine,norepinephrine,and acetylcholine levels in the prefrontal cortex.