We are investigating the effects of manganese (Mn) alone and in combination with stress when these occur during early development. This is an important area of investigation in children’s health since Mn exposure occurs in young children from soy-based infant formulas, ferromanganese industrial plants, and well water in areas with naturally occurring ground water Mn. In addition, Mn exposure is seen more often in low social economic status (SES) families.

Low SES conditions have been associated with stress, and children in these situations tend to have higher levels of circulating cortisol.
We are investigating the effects of Mn and stressors as models of low SES on the development of monoamine neurotransmitters in the brain, hormonal responses to stress, and behavior, especially learning and memory.

We find that early exposure to Mn leads to long-term changes in neurotransmitters, especially dopamine, and to spatial and egocentric learning and memory deficits. Chronic stress has similar effects. We are currently investigating the mechanisms of these effects and how these factors interact.

In addition, we have recently shown that early Mn exposure places the organism at increased risk for later development of Parkinson-like effects. After we exposed laboratory rats to Mn early in life and later give them 6-hydroxydopamine, a drug that induces Parkinson-like effects, but given at a threshold dose that does not elicit symptoms by itself, all groups show learning impairments but the combination group shows severe effects. We have a pilot grant to further understand how Mn exposure imparts increased risk for Parkinsonism.