Neonatal lead exposure in rats: I. Effects on activity and brain metals

Upon parturition, Sprague-Dawley dams were administered 1.0 (LL), 2.5 (ML), 5.0 (HL) mg/ml of lead acetate or 1.25 mg/ml sodium acetate (C) in their drinking water. Pups were weaned to tap water at 22 days of age. The developmental pattern of neonatal activity was characterized by monitoring spontaneous activity of single pups for 30 minutes on days 12, 14, 16, 18, 20, and 22, and for one hour in adults. Brains were removed at weaning for subsequent analyses of lead, zinc, and copper. The effects of lead on neonatal activity were considered to be minor because only the ML group differed significantly from C and exhibited hyperactivity on day 16. Adult activity levels, however, were decreased in a dose-dependent fashion. At 22 days of age, whole brain metal analyses revealed a dose-dependent increase in lead levels and a decrease in zinc. These results do not strongly support a hypothesis of lead-induced neonatal hyperactivity.