Lead and ethanol coexposure: implications on the dopaminergic system and associated behavioral functions

The present investigation involves ethanol's effects on the lead-induced alterations in the dopaminergic system. Ethanol, at a dose of 3 g/kg body weight for 8 weeks, resulted in a marked increase in the accumulation of lead in the blood and brain of animals receiving 50 mg lead/kg body weight. Levels of dopamine were found to decrease significantly, and were accompanied with increased norepinephrine levels in lead and ethanol coexposed animals. Uptake of tyrosine as well as the activities of tyrosine hydroxylase and monoamine oxidase were seen to increase significantly in lead as well as ethanol-treated animals, and these were increased to a greater extent when animals were administered lead and ethanol simultaneously. Dopamine receptor binding studies revealed a significant elevation in the number of binding sites in lead and ethanol-coexposed animals. The altered dopaminergic functions were reflected by the neurobehavioral deficits in terms of motor incoordination, aggressiveness, and hyperactivity of animals exposed to lead, the effect being more pronounced in lead- and ethanol-coexposed animals. In brief, results of this study suggests that ethanol potentiates lead-induced cellular damage at the neurochemical and neurobehavioral level.