Toxic Mechanisms Underlying Motor Activity Changes Induced by a Mixture of Lead, Arsenic and Manganese.

Pb, As and Mn are neurotoxic metals, present as mixtures at various settings. All metals are known to interfere with cholinergic/dopaminergic neurotransmission and motor function. The main objective of this work was to assess metal mixture effects of lead (Pb), arsenic (As) and manganese (Mn) on motor activity, and to evaluate the role of each mixture component as well as their additive/synergic interactions on dopaminergic and cholinergic neurotransmission. Wistar rats were treated with 8 doses of each single metal, Pb, As and Mn, or a triple metal mixture. Motor activity was evaluated along with cholinergic/dopaminergic neurotransmission, using brain acetylcholinesterase (AChE-Br) activity and serum prolactin (PRL-S) levels, respectively. Brain concentrations of Pb, As, Mn were also quantified. The metal mixture induced decreased motor activity relative to all other groups with factor analysis revealing close proximity between AChE-Br and motor activity. Pb brain levels increased significantly as compared to all the other groups, while β coefficients of multiple regression showed that this metal was the most effective in changing AChE-Br. Significant effects of interactions among the three metals on the activity of this enzyme were also noted for the metal mixture. In conclusion, co-exposure to Pb, As and Mn mixture alters the cholinergic system and motor activity to a greater extent than the dopaminergic system. Additive/synergic interactions between Pb, As and Mn may have a relevant role in mediating these events.