Zinc deficiency induces depression-like symptoms in adult rats

There is mounting evidence suggesting a link between serum zinc levels and clinical depression. Not only is serum zinc negatively correlated with the severity of symptoms, but zinc levels appear to be lowest in patients who do not respond to antidepressant drug therapy. It is not known if reduced zinc levels are contributing to depression, or the result of dietary or other factors associated with major depression. Thus, we designed this study to test the hypothesis that dietary zinc deficiency would induce depression-like behaviors in rats. Two-month-old male rats were fed zinc adequate (ZA, 30 ppm), deficient (ZD, 1 ppm), or supplemented (ZS, 180 ppm) diets for 3 weeks. Consistent with the development of depression, ZD rats displayed anorexia (p < 0.001), anhedonia (reduced saccharin:water intake, p < 0.001), and increased anxiety-like behaviors in a light–dark box test (p < 0.05). Furthermore, the antidepressant drug fluoxetine (10 mg/kg body wt) reduced behavioral despair, as measured by the forced swim test, in rats fed the ZA and ZS rats (p < 0.05), but was ineffective in ZD rats. Together these studies suggest that zinc deficiency leads to the development of depression-like behaviors that may be refractory to antidepressant treatment.