Effects of mercury on neurochemical receptor-binding characteristics in wild mink

Piscivorous wildlife, such as mink (Mustela vison), routinely are exposed to mercury (Hg) in their natural environment at levels that may cause adverse behavioral outcomes. The purpose of this study was to determine if a correlation exists between neurochemical receptors and concentrations of Hg in the brains of wild mink. Specifically, receptor-binding assays were conducted to characterize the muscarinic cholinergic (mACh) and dopaminergic-2 (D2) systems in brain tissues collected from mink trapped in the Yukon Territory, Ontario, and Nova Scotia (Canada), and values were correlated with total Hg and methyl Hg (MeHg) concentrations in the brains. A significant correlation was found between Hg (total Hg and MeHg) and mACh receptor density (r = 0.546; r = 0.596, respectively) or ligand affinity (r = 0.413; r = 0.474, respectively). A significant negative correlation was found between total Hg and D2 receptor density (r = -0.340) or ligand affinity (r = -0.346). These correlations suggest that environmentally relevant concentrations of Hg may alter neurochemical function in wild mink, and that neurochemical receptor-binding characteristics can be used as a novel biomarker to assess Hg's effects on wildlife. Given the importance of the muscarinic cholinergic and dopaminergic pathways in animal behavior, further studies are required to explore the physiological and ecological significance of these findings.