Behavioral effects of chronic exposure to low levels of lead in XXXX .

@entity1 @entity10222 @entity15 @entity238
Through @entity1 activity lead has become a serious environmental neurotoxin, known to affect activity levels, attention and both sensory and cognitive function in @entity1 . Study of lead would be facilitated by having a model system that could be manipulated easily and quickly. We find @entity238 ideal as such, and we have been studying effects of lead on courtship, fecundity and locomotor activity. We raised Canton-S flies from eggs to adult day 6-7 on medium made with @entity10222 solution (2-100 microgram/g), or with distilled water, and we measured adult body lead burdens by means of Inductively Coupled Plasma Mass Spectrometry (ICP- @entity15 ). To measure courtship effectiveness, five virgin females and five virgin males were transferred into an empty vial and the number of females that mated within 20min was recorded. To measure fecundity, all adult offspring from eggs produced by one female within 12 days of mating were counted. To measure locomotor activity, individual flies were transferred to a grid-labeled petri dish and the number of lines crossed in 30s was counted. The number of females mating within 20min was increased significantly by exposure to 2 or 8 microgram/g lead, and was decreased significantly by exposure to 20 or 50 microgram/g lead. Fecundity was increased significantly by exposure to 2 microgram/g lead, but was unaffected by exposure to 20 microgram/g lead. Locomotor activity was consistently higher for males than for females, and was significantly reduced only by exposure to 50 microgram/g lead, and then only for males. We thus defined for @entity238 a lowest observable effect level (LOEL) of 2 microgram/g lead, which is considerably lower than the doses shown previously to affect this animal. The dose-response curve was biphasic for the number of females mating within 20min, an example of hormesis, a non-linear response that has been reported for low levels of stressors as diverse as pollutants and radiation. We hope from further studies with @entity238 to understand better how lead affects the developing nervous system, and thus ultimately its effects on @entity1 .
