RELATIONSHIPS BETWEEN LEAD-INDUCED LEARNING IMPAIRMENTS AND CHANGES IN DOPAMINERGIC, CHOLINERGIC, AND GLUTAMATERGIC NEUROTRANSMITTER SYSTEMFUNCTIONS

Behavioral consequences of low-level lead (Pb) exposure include impair ments in learning processes and in Fixed-Interval schedule-controlled operant behavior. Although the neurobiological bases of these effects remain undetermined, current evidence suggests that inhibitory effects of Pb on the NMDA receptor complex may play a preferential role in th e learning deficits. In contrast, alterations in dopaminergic systems, consistent with a decrease in dopamine availability, appear to be rel ated to the changes in Fixed-Interval performance. Hypocholinergic fun ction has also been described, but its relationship to the behavioral changes is not yet known. Explication of these relationships will requ ire more efforts involving direct rather than correlative methods. The answers are critical for understanding risks associated with exposure and for the development of behavioral or chemical therapeutic strateg ies for dealing with lead neurotoxicity.