A novel system applying the 2-deoxyglucose method to fish for characterization of environmental neurotoxins

Methods of identifying and preventing ecotoxicity related to environmental stressors on wildlife species are underdeveloped. To detect sublethal effects, we have devised a neurochemical method of evaluating environmental neurotoxins by a measuring changes in regional neural activity in the central nervous system of fish. Our system is a unique adaptation of the 2-deoxyglucose (2-DG) method originally developed by L. Sokoloff in 1977, which is based on the direct relationship between glucose metabolism and neural functioning at the regional level. We applied these concepts to test the assumption that changes in neural activity as a result of chemical exposure would produce measurable effects on the amount of [¹⁴C]2-DG accumulated regionally in the brain of Tilapia nilatica. For purposes of this study, we utilized the excitotoxin N-methyl-D-aspartate (NMDA) to characterize the response of the central nervous system. Regional accumulation of [¹⁴C]2-DG was visualized by autoradiography and digital image processing. Observable increases in regional [¹⁴C] 2-DG uptake were evident in all NMDA-treated groups as compared to controls. Specific areas of increased [¹⁴C] 2-DG uptake included the telencephalon, optic tectum, and regions of the cerebellum, all areas in which high concentrations of NMDA-subtype glutamate receptors have been found in Tilapia monsanbica. These results are consistent with the known neural excitatory action of NMDA.