Behavioral effects and ChE measures after acute and repeated administration of malathion in rats.

Organophosphorus compounds such as malathion are environmental contaminants that may evoke neurobehavioral responses including anxiety and depression. In this study, after a functional observational battery, rats were tested in an open field and temperature test to better define doses used in subsequent experiments. Then, we investigated the effects of acute and repeated treatment with malathion on elevated plus-maze and forced-swim test, which are validated animal models to observe for anxiety- and depressive-related behaviors, respectively. We found that both acute and repeated malathion administration induced anxiogenic and depressive-like responses at doses that affected neither locomotion nor systemic temperature. Biochemical assays demonstrated inhibition of cholinesterase activity by these effective doses.