Effects of low concentrations of lead on memory and learning in rats

  Lead poisoning is the most significant preventable disease of environmental origin. Neurodevelopment is highly complex and there are numerous opportunities for lead to interfere with normal development. Lead acetate can disrupt the action of the CNS and the development of dendrites and axons. The present study was carried out to assess the effect of low-level lead exposure on memory and learning. Three groups of Wistar rats (190-220 g) were exposed to low concentrations of lead during different phases of development for a period of 21 days. Exposure was initiated at conception (group I), at parturition (group II), or after weaning (group III). The drinking water of the experimental groups was replaced by 0.05%, 0.1% or 0.2% lead acetate solution. Each test group had a control, which received double distilled water. In this behavioral study, active avoidance conditioning was used. The learning acquisition test showed decreased shocks in lead exposed as compared to control male rats in groups II and III (0.05%, 0.2%). Memory testing also showed a reduction in the number of shocks in groups II and III (0.05%, 0.2%) compared to the controls. In contrast, male rats in group I which were exposed to 0.1% lead acetate showed an increase in the number of shocks. These results were similar to GABA, which produced a depressant effect on the CNS and decreased attention in animals. Although the mechanisms of lead poisoning in the CNS are not clear, various studies suggest that lead acetate probably increases the spontaneous release of neurotransmitters in the synapse and blocks impulse conduction.