Evaluation of the effects and mechanisms of action of mercuric chloride on striatal dopamine release by using in vivo microdialysis in freely moving rats

The in vivo effects of inorganic mercury (Hg(2+)) on striatal dopamine (DA) release were studied in freely moving and conscious rats using brain microdialysis techniques. Intrastriatal administration of HgCl(2) (1mM) produced an increase in extracellular DA levels of 1717+/-375% with respect to basal levels. This effect was attenuated in a Ca(2+)-free medium (361+/-66%), after pre-treatment with reserpine (231+/-66%), and was prevented in the presence of tetrodotoxin (TTX). Thus, the HgCl(2) treatment increases striatal DA according to an external calcium and vesicular dependent mechanism, being affected by the blockade of voltage sensitive sodium channels. Moreover, HgCl(2) decreased KCl-evoked DA release. Conversely, the coinfusion of HgCl(2) with nomifensine produced increases in DA extracellular levels different to that produced by nomifensine alone, suggesting that these effects probably involve an independent DA transporter (DAT) mechanism.