Low selenium diet induces tyrosine hydroxylase enzyme in nigrostriatal system of the rat

We have studied the effect of a selenium-deficient diet on the nigrostriatal dopaminergic system for 15 and 30 days. The neurochemical analysis demonstrated significant elevations in nigral DA levels after 15 and 30 days of selenium deficiency. The most significant change in striatum was an elevation in dopamine (DA) in 30-day-deficient animals. As a further step, we measured the levels of activity and mRNA expression of tyrosine hydroxylase (TH) and dopamine transporter (DAT). There were significant elevations in all of these parameters in the nigrostriatal system following selenium deficiency at the two time-points studied except for the striatal DA uptake at day 30, which dropped to control levels. Altogether, our results suggest that the decrease in antioxidant capacity due to a selenium deficiency promotes an increase in DA synthesis and turnover, which are clearly associated to the induction of TH. This effect may trigger a positive feed-forward mechanism that could increase the oxidative stress considering the capacity of DA to generate free radicals.