OBJECTIVE: We wished to study the impact of Chaihushugan San(CSS) on the behavior of perimenopausal rats with liver-Qi stagnation(LQS) and to investigate the effect of CSS on signal transduction of the Raf/mitogen-activated protein kinase(MEK)/extracellular signal-regulated kinase(ERK) cascade in the hippocampi of rats induced by immobilization.METHODS: Twenty 52-week-old female rats were divided into two groups by the random number table method: model control group(MCG) and CSS group(CSSG), with 10 rats in each group.Ten-week-old female rats were used as the normal control group(NCG). CSS effects were assessed using rats exposed to immobilization stress by measuring body weight and sucrose consumption, serum hormone levels, and observing performance in the open field test(OFT). Molecular mechanisms were examined by measuring the effect of CSS on expression of Raf1, MEK1/2 and ERK1/2 m RNA in hippocampi using quantitative real-time polymerase chain reaction and by measuring levels of these proteins and related phospho-proteins using Western blotting.RESULTS: Perimenopausal rats with LQS had decreased locomotor activity; reduced sucrose consumption; and increased serum levels of corticotropin releasing hormone(CRH) and corticosterone(CORT). Activation of hippocampal Raf/MEK/ERK cascade was suppressed significantly in the MCG,and activation was increased after 21 days of CSS treatment.CONCLUSION: CSS has significant effects upon relief of the symptoms of LQS in immobilization-induced rats. The mechanism underlying this action might(at least in part) be mediated by reversal of disruption of the Raf/MEK/ERK pathway.