Mood-related behavioral and neurochemical alterations in mice exposed to low chlorpyrifos levels during the brain growth spurt.

We hypothesize that the brain growth spurt is a critical period concerning CPF-induced mood-related alterations on brain function, and that neurochemical and behavioral alterations would be identified even after a CPF dose that evokes negligible levels of AChE inhibition. To verify this hypothesis, we exposed neonatal mice to a subchronic low-level regimen of CPF exposure that did not result in a significant inhibition of AChE activity in the brain. We evaluated the effects CPF on mood using a battery of behavioral tests: open field, elevated plus maze and forced swimming tests. Considering the relevant association among the cholinergic system, the serotonergic system and mood disorders, we evaluated these two neurotransmitter systems in the cerebral cortex and brainstem both by the end of exposure and at adulthood. Regarding the cholinergic system, we assessed the binding of [3H] hemicholinium-3 (HC-3) to the high-affinity presynaptic choline transporter (Ch transporter) and the choline acetyltransferase (ChAT) activity. As for serotonergic system, we choose to assess 5-HT1A and 5-HT2 receptors, and the presynaptic 5-HT transporter