Enriched environment mitigates depressive behavior by changing the inflammatory activation phenotype of microglia in the hippocampus of depression model rats.

BACKGROUND: Inflammation mediated by microglia has been shown to be involved in the pathogenesis of depression. The enriched environment (EE) can improve depression-like behaviors and reduce inflammatory reactions, but it is unclear whether this is by changing the inflammatory activation phenotype of microglia. METHOD: A depression rat model was established using chronic unpredictable stress (CUS) for four weeks. The rats were then treated with EE or fluoxetine administration during the following three weeks. Behavior tests including sucrose preference, forced swimming and open field were applied to evaluate the depression-like behaviors of rats at the baseline period prior to CUS, the end of fourth week and at the end of the seventh week. Microglial activation and hippocampal neuro-inflammation were detected on postmortem using immunofluorescence, western blotting, and real-time polymerase reaction (PCR). RESULT: The results showed that severe depressive-like behavior was induced by four weeks of CUS. Changes in peripheral blood inflammatory cytokines were detected by ELISA. Immunofluorescent staining showed the IBA-1 of microglia activation marker level significantly increased in affected rats. The hippocampal microglial activation state was determined by measuring the increased levels of iNOS an M1 marker and the decreased levels of CD206, an M2 marker. The activation of NF-κB upregulation of inflammatory cytokines in the hippocampus and factors such as IL-10 were decreased. This study showed that EE and chronic fluoxetine treatment alleviated the depressive-like behavior induced by chronic stress and significantly inhibited microglial activation, activated NF-κB inflammasome and increased pro-inflammatory cytokines. CONCLUSION: EE can alleviate depression-like behavior by modulating the phenotype of microglia, inhibiting pro-inflammatory genes, and promoting anti-inflammatory genes. Furthermore, EE can effectively reduce the phosphorylation and expression levels of NF-κB.

Associations of serotonin transporter gene promoter polymorphisms and monoamine oxidase A gene polymorphisms with oppositional defiant disorder in a Chinese Han population.

BACKGROUND: Oppositional defiant disorder (ODD) is a behavioral disorder that mainly refers to a recurrent pattern of disobedient, defiant, negativistic and hostile behaviors toward authority figures. Previous studies have showed associations of serotonin transporter (5-HTT) and monoamine oxidase A (MAOA) with behavioral and psychiatric disorders. The purposes of this study were to investigate the potential association of 5-HTT gene promoter polymorphism (5-HTTLPR) and MAOA gene polymorphism with susceptibility to ODD in a Han Chinese school population. METHODS: The 5-HTTLPR gene polymorphism and the MAOA gene polymorphism were genotyped in a case-control study of 257 Han Chinese children (123 ODD and 134 healthy controls). RESULTS: There was significant difference in the allele distribution of 5-HTTLPR (χ2 = 7.849, P = 0.005) between the ODD and control groups. Further, there were significant differences in genotype (χ2 = 5.168, P = 0.023) and allele distributions (χ2 = 10.336, P = 0.001) of the MAOA gene polymorphism that is variable-number tandem repeat (MAOA-uVNTR) between two groups. Moreover, there were significant differences in genotype (χ2 = 4.624, P = 0.032) and allele distributions (χ2 = 9.248, P = 0.002) of MAOA-uVNTR only in the male ODD and healthy groups. CONCLUSIONS: Our results suggest that 5-HTTLPR and MAOA-uVNTR gene variants may contribute to susceptibility to ODD. Further, MAOA-uVNTR gene polymorphism may play a role in susceptibility to ODD only in male children.

Enriched environment combined with fluoxetine ameliorates depression-like behaviors and hippocampal SYP expression in a rat CUS model.

Effects of enriched environment (EE) combined with fluoxetine in a chronic unpredictable stress (CUS) rat model were examined in our study. Thirty male Sprague-Dawley rats were randomly divided into control group, CUS group, CUS+EE group, CUS+fluoxetine group, and CUS+EE+fluoxetine group (n=six per group). Rats in the CUS group were bred under conditions of CUS and separation for 6 weeks; Control group animals were bred in group cages (three rats per cage) under standard laboratory conditions for 6 weeks; Rats in CUS+EE group, CUS+fluoxetine group, and CUS+EE+fluoxetine groups were bred under the conditions of CUS and separation for 6 weeks and had an intervention of EE, an oral gavage of fluoxetine, and an intervention of EE+oral gavage of fluoxetine, respectively, every day for the final 3 weeks. Every rat underwent a behavioral assessment at the beginning of the 1st week, at the end of the 3rd week and at the end of the 6th week. Behavioral assessments included sucrose water consumption, weight measurement, and an open field test (measuring horizontal moving distance, rearing behavior, and defecation). Finally, the level of synaptophysin expressed in the hippocampus was measured with immunohistochemistry. We found that EE, fluoxetine, and EE+fluoxetine all reversed the depression-like behaviors of CUS rats. The effect of EE+fluoxetine appeared to be superior to EE or fluoxetine alone; the expression level of synaptophysin in CA1, CA3, and DG of the hippocampus was decreased in CUS rats, however, exposure to EE, fluoxetine, and EE+fluoxetine all reversed this decrease.

Venlafaxine ameliorates the depression-like behaviors and hippocampal S100B expression in a rat depression model.

BACKGROUND: Accumulating evidence has indicated that S100B may be involved in the pathophysiology of depression. No published study has examined the effect of the antidepressant drug venlafaxine on S100B in animal models of depression. This study investigated S100B expression in the hippocampus and assessed the effect of venlafaxine on S100B mRNA level and protein expression in rats exposed to chronic unpredictable mild stress (CUMS). METHODS: Forty Sprague-Dawley rats were randomly divided into four groups as control, 0, 5 and 10 mg venlafaxine groups. The venlafaxine groups were exposed to CUMS from day 2 to day 43. Venlafaxine 0, 5 and 10 mg/kg were then administered from day 23 to day 43. We performed behavioral assessments with weight change, open-field and sucrose preference, and analyzed S100B protein expression and mRNA level in the hippocampus. RESULTS: The CUMS led to a decrease in body weight, locomotor activity and sucrose consumption, but venlafaxine treatment (10 mg) reversed these CUMS-induced decreases Also, CUMS increased S100B protein expression and mRNA level in the hippocampus, but venlafaxine treatment (10 mg) significantly decreased S100B protein expression and mRNA level, which were significantly lower than the other treatment groups, without significant difference between the 10 mg venlafaxine and the control groups. CONCLUSIONS: Our findings showed that venlafaxine treatment (10 mg) may improve the depression-like behaviors and decrease over-expression of S100B protein and mRNA in the hippocampus in a rat model of depression.