Absence of hyperactivity in lead-exposed developing rats.

It has been reported that postnatal lead treatment produces hyperactivity in rodents. Using rats, we attempted to extend these findings. Locomotor activity of offspring of lead-intubated and pair-fed control mothers was measured at 24-27 days of age, and no significant differences in reactivity or basal activity were found. Observational scoring of the animals at 28-29 and 35-36 days of age indicated that active behaviors were slightly reduced in the lead-treated rats. The brain lead concentrations of experimental animals were slightly reduced in the lead-treated rats. The brain lead concentrations of experimental animals were significantly elevated over controls. Estimates of statistical power indicated that behavioral effects of the magnitude reported in the literature would likely have been detected. The present results indicate that low-level lead exposure may not reliably produce hyperactivity in rodents. A review of the literature suggests that other data provide little support for a recently proposed rodent model of hyperactivity in children.