Effects of developmental lead exposure on inhibitory avoidance learning and glutamate receptors in rats

Chronic lead (Pb) exposure during development is known to produce learning deficits. AMPA and NMDA receptors have been shown to participate in the synaptic mechanisms involved in certain forms of learning and memory. We investigated whether the effects of Pb on AMPA and NMDA receptors are associated with Pb-induced impairment in learning and memory. Rats were exposed to 0.2% lead acetate at different developmental stages including a maternally exposed group (including gestation and lactation period), a postweaning exposed group, and a continuously exposed group. Lead treatment impaired learning acquisition, but not memory retention in step-down avoidance learning task in all treatment groups. In parallel with the behavioral data, autoradiographic analyses of brain sections indicated that the [3H]AMPA binding was decreased in the CA1 and dentate gyrus of the hippocampus and entorhinal cortex in all three Pb-exposed groups. However, an increase in [3H]MK801 binding was only observed in CA1 of the hippocampus in the continuously Pb-exposed rats. The findings suggest that alterations in AMPA receptor may contribute to the Pb-induced deficits in learning acquisition of inhibitory avoidance.