Objective To investigate the effects of naringin (Nar) on lipopolysaccharide (LPS)-induced depression-like behaviors in mice. Methods Thirty C57BL/6 male mice (8 weeks old, SPF grade, weighting 20~23 g) were randomly divided into 3 groups (n=10): control group, saline (Sal)+LPS group, and Nar+LPS group. The mice of the last group were pretreated with Nar (80 mg/kg, i.p., once a day for 8 consecutive days). The exploratory behavior and anxiety-like behavior in mice were assessed by open field test, light and dark box experiment and elevated plus maze test. Sugar water preference test, hanging tail test and forced swimming test were used to evaluate the depression-like behaviors of the mice. Immunohistochemical assay for Iba1 was adopted to detect the effects of Nar and LPS treatments on the number of microglia in the hippocampus of mice. Western blotting and qRT-PCR were performed to determine the protein expression of NF-κB and the mRNA levels of IL-1β, TNF-α and NF-κB in mouse hippocampus, respectively. Results As compared with the control group, the mice in the Sal+LPS group showed decreased preference for sugar water (P < 0.05), and increased immobile time in the forced swimming test (P < 0.01) as well as in the hanging tail test (P < 0.05). The number of microglia in the hippocampus was elevated (P < 0.01), the protein level of NF-κB and the mRNA levels of IL-1β, TNF-α and NF-κB were also up-regulated (P < 0.05). When compared with the Sal+LPS group, the mice in the Nar+LPS group presented increased preference for sugar water (P < 0.01), and decreased immobility time in the forced swimming test (P < 0.01) and hanging tail test (P < 0.05), with higher number of microglia in the hippocampus (P < 0.01), and lower protein levels of NF-κB and mRNA levels of IL-1β, TNF-α and NF-κB (P < 0.01). Conclusion Nar may ameliorate LPS-induced depression-like behaviors in mice by inhibiting inflammation in the hippocampus.
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