Neonatal lead exposure: effects on development of behavior and striatal dopamine neurons

Rats treated directly with water or lead acetate (25 or 75 mg/kg) on postnatal days 2 through 14 were tested for the development of spontaneous activity and for locomotor responses to d-amphetamine as weanlings. The development of striatal dopamine (DA) levels, uptake, release, and the disappearance of DA after synthesis inhibition were also examined. Blood and brain levels were markedly increased at 15 days in exposed animals; by 35 days blood lead levels had decreased 90% while lead level in neostriatum decreased only 55-60%. The effects of the early lead exposure fell into two classes. Shortly after cessation of lead treatment, changes were observed in exposed animals in the development of motor activity, as well as in the disappearance of DA after synthesis inhibition, accumulation of labelled DA, and endogenous DA levels. As brain lead decreased from 15 to 35 days many of the behavioral and neurochemical abnormalities also dissipated. However, at 35 days, striatal DA levels remained decreased in animals given the higher lead dose with a resultant decrease in turnover rate and alterations were noted in activity responses to d-amphetamine in lead-treated animals.