Motor development, tissue weights and seizure susceptibility in perinatally lead-exposed rats

Motor impairments and seizures are frequent neurologic sequelae of excess lead exposure in children. To evaluate the relative significance of such symptoms in an animal model, Long-Evans rats were lead-exposed from parturition to weaning by adulteration of the dams' drinking water with 0.02% or 0.2% lead acetate. Ontogeny of swimming ability from 6 through 24 days of age was not altered by postnatal lead exposure. Rotorod performance was tested on 21, 30, 60, 90, 150 and 440 days of age and was maximal in rats 30 through 150 days of age, with the poorest performance by 440-day-old rats. Rotorod performance was decreased by both levels of lead exposure and this effect was most evident at 60 and 150 days of age. Both levels of lead exposure increased kidney weights of dams at weaning and the 0.2% lead acetate exposure decreased hematocrit of dams. Kidney weights of lead-exposed pups were not increased at 10 days of age, but pups in the 0.2% lead acetate group had increased kidney weights at 20, 90 and 150 days of age. Hematocrit values of pups in the 0.2%, but not in the 0.02%, lead acetate exposure group were decreased at 20 days of age. No effects of lead exposure on hematocrits were found at 10, 90 or 150 days of age. Wet weight of brain, cerebellum, adrenals, spleen and thymus were not altered at any age by postnatal lead treatment. In a second study, Sprague-Dawley rats exposed to lead via dams drinking 0.2% lead acetate throughout gestation and lactation. Pre- and postnatal lead exposure did not alter the ontogeny of electro-shock seizure thresholds in rats tested on 8 through 20 days of age. The results suggest that the lead exposure levels used were at or near a no-effect level for several common neurobehavioral tasks and that kidney weight may be a more discriminative index of excess lead exposure than some simple neurobehavioral indices.