RESULTS

Effects on open-field activity scores in open-field test
Open-field activity was measured 3 times during the experimental period [Figure 1]. In the open-field test, there were no significant differences in the number of crossings and rearings among all groups before stress (F(3,36) = 0.108, P > 0.05 and F(3,36) = 0.031, P > 0.05, respectively). Rats in model group showed a significant decrease in the number of crossings and rearings after 2-week stress compared with the normal control group (P < 0.01), which continued to the 4th week when the experiment was closed (P < 0.01). In both of drug treated groups, the number of crossings and rearings decreased significantly after 2-week exposure to stressor (P < 0.01) and show a significant increase compared with the model group after 2-week treatment (P < 0.01) and did not show significant differences in these behavioral changes between CHSGS group and fluoxetine group after 2-week treatment (P > 0.05).
Figure 1  Open-field activity of rats. Rats were administrated with Chaihu-Shugan-San or fluoxetine for 2 weeks after 2-week exposure to the stressor. The open-field test was carried out before stress (0 week), 2 weeks after stress (2 week) and 4 weeks after stress (4 week). (a) Number of crossings during the 3 min session. (b) Number of rearings during the 3 min session. Values are the means ± standard error of mean (n = 10). **P < 0.01, as compared with the normal control group;##P < 0.01, as compared with the model group

Effects on sucrose consumption
Sucrose consumption was measured 3 times during the experimental period [Figure 2]. Before stress, there were no significant differences among the four groups (F(3,36) = 0.797, P > 0.05). After 2-week stress, the sucrose consumption in stressed rats was significantly lower than that in the normal control group (P < 0.01). After 2-week exposure to stressor the sucrose consumption in the CHSGS and fluoxetine groups was significantly lower than that in the normal control group (P < 0.01) and show a significant increase compared with the model group after 2-week treatment (P < 0.01).
Figure 2  Sucrose consumption of rats. Rats were administrated with Chaihu-Shugan-San or fluoxetine for 2 weeks after 2-week exposure to the stressor. The sucrose consumption test was carried out before stress (0 week), 2 weeks after stress (2 week) and 4 weeks after stress (4 week). Results are expressed as the means ± standard error of mean (n = 10). **P < 0.01, as compared with the normal control group;##P < 0.01, as compared with the model group

The levels of P-ERK1/2 and total ERK1/2 in the hippocampus
The signals of β-actin, P-ERK1/2 and ERK1/2 were detected in the hippocampus [Figure 3]. There were significant differences among groups in the hippocampus in the levels of p-ERK1/2 (F(3,16) = 7.352, P < 0.01 and F(3,16) = 3.432, P < 0.05, respectively) [Figure 4a]; CMS rats showed a significant decrease in the levels of P-ERK1/2 in the hippocampus as compared with normal group (P < 0.01 and P < 0.05, respectively); administration of CHSGS (5.9 g/kg/body wt.) for 14 days increased levels of p-ERK1/2 in the hippocampus as compared with the model control group (P < 0.01 and P < 0.05, respectively); the positive control, fluoxetine (1.8 mg/kg/body wt.) also increased levels of P-ERK1/2 significantly (P < 0.01 and P < 0.05, respectively) and there were no significant differences in the levels of P-ERK1/2 between CHSGS group and Fluoxetine group (P > 0.05, either). However, for the levels of ERK1/2, no significant difference was observed among groups in the hippocampus (F(3,16) = 1.390, P > 0.05 and F(3,16) = 0.850, P > 0.05, respectively) [Figure 4b].
Figure 3  Representative western blots of phospho-extracellular signalregulated kinase (P-ERK1/2), total ERK1/2 and their corresponding normalized control β-actin in hippocampus. (1) Normal group; (2) model group; (3) Chaihu-Shugan-San group; (4) fluoxetine group
Figure 4  The levels of phosphor-extracellular signal-regulated kinase (P-ERK1/2) (a), ERK1/2 (b) and the ratio of P-ERK1/2 to total ERK1/2 (c) in hippocampus. All data were expressed as mean ± standard error of mean (n = 5/group). **P < 0.01 compared with normal group. *P < 0.05 compared with normal group.##P < 0.01 compared with model group.#P < 0.05 compared with model group   There were significant differences among groups in the hippocampus in the ratio of P-ERK1/ERK1 and P-ERK2/ERK2 (F(3,16) = 3.327, P < 0.05 and F(3,16) = 3.572, P < 0.05, respectively) [Figure 4c]; the CMS rats had a marked decrease in the ratio of P-ERK1/ERK1 and P-ERK2/ERK2 (P < 0.05, either); CHSGS or fluoxetine had a reversing effect on the stress-induced decrease in the ratio of P-ERK1/ERK1 and P-ERK2/ERK2 (CHSGS: P < 0.05 and P < 0.01, respectively; fluoxetine: P < 0.05, either) and there were no significant differences in the ratio of P-ERK1/ERK1 and P-ERK2/ERK2 between CHSGS group and Fluoxetine group (P > 0.05, either).