The neurotoxic effects of heavy metal exposure on GABAergic nervous system in nematode Caenorhabditis elegans.

The number of cell body or synapse made by Caenorhabditis elegans GABAergic neurons is constant during development. The neurotoxic effects of metal (Pb, Hg, Cu, Cd, Cr, and Mn) exposure on GABAergic motor neurons were investigated in C. elegans. Exposure to examined metals could not alter the position of GABA neurons, whereas exposure to high concentrations (75μM and 200μM) of metals caused noticeable axonal degeneration and neuronal loss in nerve cords, suggesting neurodegeneration will be induced by metal exposure to different degrees. In addition, exposure to Pb, Hg, Cu, and Cd at the low concentration (2.5μM) could also induce obviously neuronal loss. Moreover, exposure to high concentrations (75μM and/or 200μM) of most of examined metals significantly reduced the relative size and fluorescent intensities of AVL, RMEs, and RIS neurons. Therefore, the neurodegeneration and abnormal structures may be formed in GABAergic motor neurons after metal exposure, and the endpoint of neuronal loss will be useful for the neurotoxicity assessment from trace metal exposure.