Behavioral effects of early lead exposure and subsequent toxocariasis in mice.

Mice were maintained under standard conditions, or treated with lead from birth, until they were approximately 40 d of age. At that time the lead solution was replaced with tap water and all animals were gastrointestinally intubated with either the parasite Toxocara canis or normal saline. At 2-5 wk following intubation the behavioral effects of T. canis in combination with the prior history of lead ingestion were compared to those produced by administration of either T. canis or lead alone or a single saline intubation. Differential group activity scores (cage crosses and standups) in response to changes in the home-cage environment during testing sessions were observed. While the addition of a second tier to the home cage during testing resulted in increased activity scores for all groups, changing the home-cage bedding produced increased activity only in the T. canis alone or prior lead ingestion alone groups. However, there were no differences in the number of parasite larvae found in fresh brain tissue preparations in either the T. canis alone or T. canis plus lead-history combination groups.