THE EFFECTS OF METHYLMERCURY ON ENDOGENOUS DOPAMINE EFFLUX FROM MOUSESTRIATAL SLICES

The present study investigated the effects of in vitro methylmercury ( MeHg) exposure on endogenous dopamine (DA) efflux from mouse striatal slices. MeHg produced a concentration-dependent increase in the sponta neous efflux of DA which was independent of the availability of Ca2+ i n the superfusion medium. The Ca2+-dependent K+-evoked release of DA w as significantly enhanced by 50 and 100 mu M MeHg. This increase could not be solely accounted for by the MeHg-induced increase in spontaneo us DA efflux. The K+-stimulated efflux of DA was enhanced by MeHg in b oth the presence and absence of Ca2+ in the superfusion medium, sugges ting that under depolarizing conditions, DA efflux induced by MeHg has a Ca2+-independent component. The alterations in DA efflux occurred a t concentrations of MeHg previously found in the CNS of animals exhibi ting symptoms of MeHg intoxication suggesting that alterations in DA n eurotransmission in the striatum may contribute to the symptoms of MeH g toxicity.