Chronic exposure to low-levels of lead in the rat: biochemical and behavioural changes

The prevalence of lead in the environment is a cause of continuing toxicology concern and there have been numerous human and animal studies to examine more thoroughly the possible consequences of exposure to this ecotoxicant. Because lead is highly toxic to the developing central nervous system, increasing concern over the rise in the lead content in the environment has been expressed. These concerns seem appropriate since more recent clinical studies have shown that prolonged exposure of children to so called 'subclinical' concentrations of lead may be associated with behavioural disorders, learning disabilities and mental retardation. Moreover, animal studies have shown that chronic perinatal low-level lead exposure elicits alterations in both learned and spontaneous behavioural patterns in the absence of typical outward signs of lead-induced neurological toxicity. No study however could relate behavioural changes to specific alterations in neurochemisty. The aim of this study was therefore to expose rats, in different stages of their development, to low-levels of lead in order to induce behavioural disorders and correlate latter with possible neurochemical changes. In accordance with the general aims of the study, the structuring of the thesis is as follows: (a) a discussion of the neurotransmitters in the brain in order to describe the different systems which have been investigated; (b) a review of appropriate literature regarding the kinetics, toxodynamics and neurotoxicity of lead and (c) a summary of the methods employed in the study. The following results are presented: (d) the effects of lead treatment on physical development of the rats; (e) the induction of behavioural supersensitivity and (f) the effects lead has on central receptors