EFFECTS OF ORAL-EXPOSURE TO MINING WASTE ON IN-VIVO DOPAMINE RELEASE FROM RAT STRIATUM

Several single components of mining waste (arsenic, manganese, lead, c admium) to which humans are exposed at the mining area of Villa de la Pat, Mexico, are known to provoke alterations of striatal dopaminergic parameters. In this study we used an anima model to examine neurochem ical changes resulting from exposure to a metal mixture. We used micro dialysis to compare in vivo dopamine release from adult rats subchroni cally exposed to a mining waste by oral route with those from a contro l group and from a sodium arsenite group (25 mg/kg/day). We found that arsenic and manganese do accumulate in rat brain after 2 weeks of ora l exposure. The mining waste group showed significantly decreased basa l levels of dihydroxyphenylacetic acid (DOPAC; 66.7 +/- 7.53 pg/mu l) when compared to a control group (113.7 +/- 14.3 pg/mu l). Although ba sal dopamine release rates were comparable among groups, when the syst em was challenged with a long-standing depolarization through high-pot assium perfusion, animals exposed to mining waste were not able to sus tain an increased dopamine release in response to depolarization (mini ng waste group 5.5 +/- 0.5 pg/mu l versus control group 21.7 +/- 5.8 p g/mu l). Also, DOPAC and homovanillic acid levels were significantly l ower in exposed animals than in controls during stimulation with high potassium. The arsenite group showed a similar tendency to that from t he mining waste group. In vivo microdialysis provides relevant data ab out the effects of a chemical mixture. Out results indicate that this mining waste may represent a health risk for the exposed population.