Abstract: ObjectiveTo investigate the alteration of behavior,such as spontaneous movement,spatial memory ability and cholinergic M receptors in the brain of mice subjected to chronic mild stress (CMS). And to determine whether Ningshen Ling (NSL)and dehydroepiandrosterone(DHEA)could reverse the cognitive impairment in this model.MethodsForty mice were divided into four groups: control group,CMS group,CMS+NSL(p.o.5g·kg^-1·d^-1) group and CMS+DHEA (i.p.5 mg·kg^-1·d-1) group. Morris water maze procedure was used to determine the spatial memory ability. M receptor binding activity was measured with radioactivity assay by³ H-QNB.ResultsAfter 3 weeks CMS,the mice exerted a decrease in spontaneous movement test,and the latency in Morris water maze was obviously prolonged. Treating CMS mice with NSL and DHEA for 1 weeks could improve the spontaneous movement and latency declined. Whereas the³ H-QNB binding ability to M receptor showed a significantly decrease in cerebral cortex and hippocampus of CMS mice (P<0.05),the decreased ability of M receptor binding was reversed by NSL treatment in hippocampus(P<0.05).ConclusionNSL and DHEA can alleviate the stress response and reversed cognitive impairment induced by CMS,and it may be concerned with the central cholinergic M receptors activity.

Key words: chronic mild stress (CMS), Ningshen Ling (Chinese herbs), dehydroepiandrosterone (DHEA), central cholinergic M receptor, spontaneous movement, Morris water maze, mice