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.