Strain difference in learning impairment in rats following lead administration during brain development

Abstract

High and stable avoidance with low variability (THA) rats and non-select Wistar rats were administered 2 mg/ml lead acetate solution (0.2-0.27 g/Kg/day as lead) up to seven weeks of age; via placenta from the 13th day of gestation and from maternal milk before weaning, and per os after weaning. Results were as follows. 1) Significant differences were not observed between the lead-exposed rats and the controls regarding the developmental landmarks in both the Wistar rats and THA rats. Body weight of the exposed rats, however, were significantly less than that of the controls of the two rat strains. 2) Low rate of avoidance, slow acquisition of learning and large individual variabilities were exhibited in both the controls and the exposed rats of the Wistar strain throughout the test sessions. No significant difference was indicated between the controls and the exposed rats of the Wistar strain. In the control THA rats, avoidance learning was acquired rapidly, and a high level and very small individual variabilities of avoidance were demonstrated during the latter sessions of the test. Meanwhile, in the exposed THA rats, slow learning acquisition and large individual variabilities were displayed. It is thought that the learning impairment appearing in the THA exposed rats was induced primarily by lead.