Neurobehavioral and neurochemical abnormalities of pre- and postnatally lead-exposed rats: zinc, copper and calcium status

Although diverging opinions have been expressed, there is a body of evidence of a cause-effect relationship between chronic exposure to lead and altered behavior in children. There are several problems in the interpretation of the behavioral and biochemical anomalies described in experimental models of lead intoxication due mainly to the different experimental conditions used. One of the major criticisms is linked with the claim that in several studies too high levels of exposure were used, hence inducing the suspicion that the effects specifically attributed to lead intoxication could be related to unspecific actions. Here we report that, using an experimental model of pre- and postnatal intoxication of rats exposed to a very low amount of lead (1 mg/kg/day), in parallel with behavioral anomalies, there are slight changes in cerebral dopaminergic and GABAergic receptors. A new finding was the discovery that in this condition there is a markedly increased number of opiate receptors in the hypothalamus (and other brain areas) in parallel with a decrease of beta-endorphin and an increase of Met-enkephalin. Therefore, low levels of lead intoxication which could be pertinent to the human situation, seem to induce neurotoxic effects which may be responsible for the behavioral anomalies in rats and, maybe, in children.