Nowadays environmental pollutants have not only increased in quantity but also changed dramatically in quality. In other words, the release of hazardous waste materials into the environment poses serious risks in humans and ecosystem. In order to minimize their environmental risks caused by the wastes the developed countries have established systems for toxicity evaluation of hazardous chemicals, legislation for their proper management plan, and their efficient administration program. Ecological risk is equivalent to product of exposure and hazard of specific chemical or a mixture of chemicals. The risk assessment, therefore, requires a comprehensive measurement of exposure and hazard of the chemicals that can be achieved by toxicity evaluation using a biological system. The biological system includes biomarkers that are molecular and physiological indicators of chemical stress.
Diazinon[O,O-diethylO-(2-isopropyl-4-methyl-6-pyrimidinyl) phosphorothioate], is an organo-phosphorous insecticide widely used for the control of agricultural and household pests, the toxic effects of which are mainly due to the inhibition of cholinesterase. Diazinon shows a high toxicity to organisms, especially fish and aquatic invertebrates although it has relatively low toxic effects on mammals and humans.
In this study we have tried to develop a biomarker used to elucidate a molecular basis of, and to monitor abnormal behavior caused by diazinon in Japanese medaka (Oryzias latipes) as a model organism. For monitoring experiments at behavioral and molecular biological levels, the fish were treated under different sublethal conditions of diazinon and their behavioral responses were observed.
Organ or tissue-specific detection of TH activity and mRNA as biomarkers will be a useful monitoring tool for neurobehavioral changes in fish influenced by toxic chemicals. Furthermore, quantitative analysis of locomotive patterns and its correlation with the neurochemical and molecular data would be highly useful in measuring toxicity and hazard of various environmental pollutants. This study provides molecular and neurobehavioral bases of a biomonitoring system for toxic chemicals using a model organism such as fish.