In Vivo Effects of Inorganic Mercury (HgCl2) on Striatal Dopaminergic System

In the present study, the effects of intrastriatal administration of different concentrations (40 μM, 400 μM, and 4 mM) of inorganic mercury (HgCl2) on the dopaminergic system of rat striatum were evaluated, using a microdialysis technique coupled to liquid chromatography-electrochemical detection. In previous studies, we discussed the effects of organic mercury (MeHg) administration on the striatal dopaminergic system on the basis of changes in the release and metabolism of striatal dopamine (DA). In the present study it is demonstrated that intrastriatal administration of all concentrations of HgCl2 produced significant increases in the output of DA (1240, 2500, and 2658% for the concentrations of 40 μM, 400 μM, and 4 mM HgCl2, respectively) from rat striatal tissue, associated with significant decreases in striatal levels of its metabolites dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) with the concentrations of 400 μM and 4 mM HgCl2 (74.4 and 3.4% for DOPAC and 71.0 and 50.6% for HVA, respectively), whereas no changes in metabolite levels were observed with the concentration of 40 μM HgCl2. These effects are explained as a result of stimulated DA release and/or changed DA metabolism. The effects of intrastriatal administration of HgCl2 were compared with those of MeHg on DA extracellular levels.