Neurotoxicants and central catecholamine systems

The ubiquitous functional roles of brain catecholamines have led to the notion that in vitro neurochemical changes in these systems may predict neurotoxicity. Conversely, others have argued that the appropriate use of neurochemical methods is for testing specific hypotheses that are developed based on observed phenomena. Three studies from this laboratory are presented in support of the latter hypothesis. The first example is with inorganic lead, a major environmental pollutant. The effects of small doses of lead on CNS development have been difficult to quantify or study mechanistically. However, the serendipitous finding that lead exposure during early postnatal development increased lithium-induced polydipsia (LIP) has provided clues that have permitted testing of specific neurochemical hypotheses related to dopamine systems. Conversely, the administration of either trimethyl- or triethyltin to rats during perinatal periods causes profound neurotoxicity. However, although some changes in the neurochemistry of catecholamine systems have been found, these data have provided little insight into either the cause or sequelae of toxicity. Finally, the food color erythrosin (FD & C Red #3) was hypothesized to be a neurotoxicant because it disrupted neurotransmitter uptake in vitro. Our data suggested this was an artifact of the methodology, a position supported by clinical and behavioral studies. These data provide examples of the strengths and weaknesses in neurochemical approaches to neurotoxicity.