Antidepressant‐like effect of flaxseed in rats exposed to chronic unpredictable stress

INTRODUCTION: Depression is a serious mental illness. However, a significant proportion of patients with depression fail to achieve remission with antidepressant therapies. This study was conducted to explore the antidepressant‐like effect of flaxseed oil and flour in an animal model with depression‐like behaviors induced by chronic unpredictable stress (CUS). METHODS: Rats were randomly divided into five groups: normal control (Sham–Sham), CUS plus saline (S‐SN), CUS plus escitalopram (S‐Esc), CUS plus flaxseeds oil (S‐FO), and CUS plus flaxseed flour (S‐FF). Behaviors were tested using sucrose preference test and forced swimming test. The serum BDNF concentration, hippocampal BDNF mRNA, and protein expression were measured by enzyme‐linked immunosorbent assay, real‐time PCR, and Western blot, respectively. RESULTS: The sucrose preference rate was significantly higher in S‐FO and S‐FF rats than in S‐SN and S‐Esc rats (p < .01), and lower in S‐Esc rats than in Sham–Sham rats (p < .01). The immobility time was significantly shorter in S‐FO and S‐FF rats than in S‐SN rats (p < .01), and shorter in S‐Esc rats than in S‐SN rats (p < .01). Plasma BDNF concentrations were significantly lower in S‐FO, S‐FF, and S‐Esc rats than in Sham–Sham rats (p < .01); BDNF was lower in S‐FO, S‐FF, and S‐SN rats than in S‐Esc rats. The hippocampal BDNF protein expression was significantly higher in S‐Esc rats than in S‐SN rats (p < .05). The hippocampal BDNF mRNA expression was significantly higher in S‐Esc rats than in S‐SN rats (p < .01). The BDNF gene expression in plasma and the hippocampus negatively correlated with the immobility time (p < .05), but BDNF gene expression in the hippocampus positively correlated with the sucrose preference rate (p < .05). CONCLUSION: Flaxseed oil and flaxseed flour exert antidepressant‐like effect in rats exposed to chronic stress. Flaxseed may have a therapeutic effect on depression.