Behavioral effects of postnatal lead exposure: Possible relationship to hippocampal dysfunction

Abstract

A review of previous evidence suggested the possibility of hippocampal involvement in the behavioral changes observed following postnatal lead (Pb) exposure. To further assess this possibility, Long—Evans hooded rat pups were exposed to inorganic Pb from postnatal Days 1 to 25 via the maternal milk. Mothers were fed diets containing either 4.0% PbCO 3 , 0.4% PbCO 3 , or a 2.2% Na 2 CO 3 control diet throughout this period. Animals were tested at maturity in four situations considered sensitive to hippocampal dysfunction. Exposure to Pb resulted in delayed acquisition of the radial eight-arm spatial maze, but produced no changes in either the susceptibility to audiogenic seizures or the acquisition and performance of a two-way active avoidance response. Pb-exposed animals were also observed to perform deficiently on a DRL-20 schedule of operant reinforcement, although significant variation was observed between litters in the Control group on this task. The results of this study are discussed in terms of a relationship between postnatal Pb exposure and hippocampal dysfunction. However, other forms of central nervous system alterations have been observed to result from early Pb exposure and alternative explanations for these behavioral changes are also suggested.