| Toluene is an important product of chemical industry, it has been used in industry and daily life. Moreover, toluene is the main air pollutant in the chamber of submarines at active service in China, lots of people were exposed to it and its hazards have been recognized by domestic and overseas researchers. But most of focus is on the neurotoxicity of toluene. Although many countries have worked out occupational hygienic standard, the toxic effect on the central nervous system (CNS) of the exposed persons still occurred under such standard. And there aren't any effective measures for prevention and treatment of the adverse effects exerted by toluene. All of these are due to the unclearness of neurotoxic mechanisms of toluene. The present study profoundly discussed the biological mechanisms of neurotoxicity of toluene in vivo and in vitro so as to provide scientific data for amending hygienic standard, assessing the risk of occupational hazard of toluene and more effectively protecting and improving health of exposed persons.1. Effects of toluene on CNS of the repeatedly exposed rats.In this part, the changes in morphology, biochemistry, function of glutamate transporters and NOS gene expression of rat's CNS caused by toluene were studied.1.1 Effects of toluene on general body state.It is known that the nervous system is susceptible to any adverse changes in environment. In neurotoxicity study These confounding factors might interfere with the analysis of toxic effects caused by neurotoxic substances if not dealt with properly. So in the present study, by i.p administration of toluene (the dose being 75mg/kg bodyweight for low dose group, 150mg/kg bodyweight for medium dose group, and 300 mg/kg bodyweight for high dose group), the rat's general body state was observed to determine the reliability of the model of neurotoxicity caused by toluene.Effect on rat's general body state In toluene-administered groups, only few animals in high dose group decreased activity, the others acted as normal. Animals in all groups took food normally, and the fur was glossy.Effect on bodyweight It could be seen from the varying curve of rat's body weight after being administered with toluene that the increase of rat's body weight in all exposed groups was basically the same as the control one. The results showed that the rats' body development was not affected as far as the present administering conditions were concerned.Effect on abdominal cavity In animals of exposed groups, no hydrops in rats' abdominal cavity was found, the abdominal wall was slippery without adhesion. And pathological examination found no inflammation cells permeating into peritonaeum. The results showed that the i.p injection didn't result in peritonitis in the rats.Because of its high volatility, toluene enters human body mainly via inhalation through respiratory tract in daily life and production. The study used the i.padministration just because i.p manner was more easily operated and the concentration could be easily controlled compared with inhalation. Because toluene is highly lipid soluble it can be rapidly absorbed through peritonaeum. But its limitations are that it was not the same as actual exposure route in human environment. But the present study only discused mechanisms but threshold concentration, so the manner could still be applied. As a nonpolar organic solvent, toluene might induce peritonitis via i.p administration. But the examination showed no peritonitis in rats , thereby eliminating the confounding effects on the results in further study.In conclusion, the administration condition and animals used in the present study conformed to the trial requirement and could be used in further study on neurotoxicity of toluene aand discussion on its mechanisms.1.2 Effects of toluene on pathological morphologyThere are two kinds of neurocytes in CNS. One is neuron, and the other is gliacyte. Influenced by the inherent idea considering the gliacyte as playing minor role in the brain but thinking of neuron as playing leading...
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