Effect of salvianolic acid on behaviors and brain inflammatory factors in depression model rats / 中华行为医学与脑科学杂志

ABSTRACT

Objective:To investigate the effect of salvianolic acid on depressive behavior in depression model rats induced by chronic mild stress (CMS) and its mechanism.Methods:Fifty healthy male clean grade Sprague-Dawley(SD) rats were divided into five groups according to a random number table with 10 in each group control group (nCMS+ Nal group), CMS+ normal saline group (CMS+ Nal group), CMS+ fluoxetine group (CMS+ Flu group), CMS+ salvia acid group (CMS+ Sal group), CMS+ fluoxetine+ Salvia acid group (CMS+ Flu+ Sal group). Except the control group, the rats in the other four groups were all received CMS modeling for 21 days. Twenty-one days after CMS modeling, rats were intraperitoneally injected with 0.9% normal saline (10 mg·kg -1·d -1), fluoxetine (20 mg·kg -1·d -1), salvia acid(40 mg·kg -1·d -1), fluoxetine(20 mg·kg -1·d -1)+ salvia acid(40 mg·kg -1·d -1)for 21 days. During the administration period, rats in the other four groups continued to receive CMS intervention for 21 days. Forced swimming test and sucrose preference test were conducted at baseline (day 0), after modeling (day 21) and after intervention (day 42) so as to evaluate depression like behavior. Then the rats were sacrificed and the hippocampus and prefrontal cortex were taken. The mRNA levels of Toll like receptor 4 (TLR4) and myeloid differentiation primary response 88 (MyD88) were detected by RT-qPCR. The cytokines including interleukin-1β(IL-1β), interleukin-2(IL-2), interferon-γ (IFN-γ) and tumor necrosis factor-α (TNF-α) were detected by Luminex technique.SPSS 21.0 was used for statistical analysis.Repeated measurement ANOVA was used for behavioral data analysis, one-way ANOVA was used for molecular index data analysis, and Spearman was used for correlation analysis. Results:The results of repeated measurement ANOVA showed that the interaction effects between group and time of body mass, sucrose preference, forced swimming immobility time were significant at baseline, after modeling and after intervention ( F=18.238, 6.921, 7.591, all P<0.05). After modeling, compared with nCMS+ Nal group, the rats in CMS+ Flu group, CMS+ Sal group, CMS+ Flu+ Sal group and CMS+ Nal group had lower body weight, lower sucrose preference rate and longer forced swimming immobility time (all P<0.05). After intervention, compared with CMS+ Nal group(body weight (350.15±41.65)g, sucrose preference(52.95±11.13)%, static time(91.40±15.22)s), the body weight((378.21±30.78)g, (385.12±43.19)g, (391.41±31.21)g, (402.33±18.67)g, all P<0.05) and sucrose preference((69.30±15.56)%, (68.12±10.99)%, (71.18±9.51)%, (75.47±11.55)%, all P<0.05) of CMS+ Flu group, CMS+ Sal group, CMS+ Flu+ Sal group and nCMS+ Nal group were all increased, while the forced swimming immobility time ((68.81±21.74)s, (66.10±25.51)s, (63.53±22.32)s, (71.21±21.41)s, all P<0.05) were shorter (all P<0.05). After intervention, among the body weight, sucrose preference and the immobility time of CMS+ Flu group、CMS+ Sal group and CMS+ Flu+ Sal group, there were no differences between each two groups(all P>0.05). After intervention, the levels of TLR4 mRNA and MyD88 mRNA in prefrontal cortex and hippocampus of CMS+ Flu group, CMS+ Sal group, CMS+ Flu+ Sal group and nCMS+ Nal group were all lower than those in CMS+ Nal group (all P<0.05). In prefrontal cortex, the levels of TLR4 mRNA (0.715±0.358) and MyD88 mRNA (0.739±0.233) in CMS+ Flu+ Sal group were lower than those in CMS+ Sal group (1.943±0.606, 1.815±0.897) (both P<0.05). The level of TLR4 mRNA in prefrontal cortex and hippocampus of rats were positively correlated with the level of MyD88 mRNA and TNF-α level and forced swimming immobility time and negatively correlated with sucrose preference rate (prefrontal cortex r=0.915, 0.041, 0.027, -0.178, all P<0.05; hippocampus r=0.810, 0.070, 0.011, -0.153, all P<0.05). Conclusion:The antidepressant effect of salvianolic acid is presumedly achieved by inhibiting the immunoinflammatory response mediated by the TLR4/Myd88 signaling pathway in CMS rats.