We have studied the turnover of dopamine, noradrenaline, and serotonin and their metabolites in hippocampus of adult female rats that were fed control or selenium-deficient diets during 15 days. Under these circumstances, there was an increase of dopamine turnover (4-fold) in rats fed with selenium-deficient diet with respect to controls and also an increase in the tyrosine hydroxylase activity (75.8%), which was the result of the increase of the amount of the enzyme (2-fold), without significant change in the phosphorylation of the tyrosine hydroxylase. In addition the glutathione peroxidase, glutathione reductase, catalase, and superoxide dismutase activities have been studied. After selenium-deficient diet, the enzymatic activities of superoxide dismutase and catalase did not show change with respect to the controls; however glutathione reductase and glutathione peroxidase significantly decreased 15% and 29%, respectively. It is concluded that the increase in dopamine turnover seems to be associated with the induction of tyrosine hydroxylase enzyme. In these conditions the decrease in antioxidant capacity may produce a cascade of events, which accelerates the degenerative process, since the increase in dopamine turnover produces an increase in oxygen radical by monoamine oxidase activity.