Mechanism Of The Release And Transmission Block Of Neurotransmitter Glu And GABA Induced By Benzo(a)pyrene

Benzo[a]pyrene is one of the Polycyclic Aromatic Hydrocarbon, whichfrom widely sources. The major source is incomplete combustion of highmolecular compound like coal and oil. Benzo[a]pyrene plays a vital role inthe Environmental Toxicology and the prevention and control ofoccupational disease. Previous study focused on the carcinogenesis,teratogenesis and mutagenesis but the neurotoxicity and developmentalneurotoxicity of PAHS gained more attentions. Study on the PAHS onneurodevelopment revealed that B[a]P can cause damage on nerve in youngSD rat. The major damage located in hippocampus which affects the spatiallearning memory. The damage is positively correlated with the change ofrelease and transition of neurotransmitter during the neurodevelopment.Glu and GABA are important neurotransmitter in the central nerve systemand have vital function in the memory formation. But whether thedevelopmental neurotoxicity induced by B[a]P is correlated with the Gluand GABA is still unclear. This study aims to reveal the mechanism underthe change of release and transmission of neurotransmitter after exposure to B[a]P.Object: based on the previous study about neurobehavioral change inyoung SD rat which exposure to B[a]P during neurodevelopment, westudied the developmental neurotoxicity of B[a]P by analyzing the changeof the release and transmission of Glu and GABA in exposed SD young rat.Methods: choose48male and48female5days old young SD rat whichin good condition and the body weight variation less than10%mean. Ratwere randomly assigned into control,0.02、0.2、2mg／kg·KW B[a]Pgroups. Solute the B[a]P in vegetable oil and gavage daily according to thedosage of the four groups. Corresponding vegetable oil was used in thecontrol group and the time of treatment various from PND4to PND20.Immunohistochemical analyze the change of neurotransmitter Glu andGABA at hippocampus and check the morphology change of roughendoplasmic reticulum, Golgi body, myelin sheath and synapse athippocampus by electronic microsope. Determine the concentration ofcalcium ion in the hippocampus synapse by commercial kit. The expressionlevel of SD、Syntaxin and SNAP at front membrane of hippocampussynapse were detected by Western Blot. qPCR was employed to determinethe quantity of neurotransmitter receptor GABA、NMD and AMPA at theback membrane of the hippocampus synapse.Result:1. IHC result shown that the expression of GABA and Glu inB[a]P groups decreased significantly compared to control group in hippocampus.2. Calcium fluorescence quantitative detection result shownthat calcium ion concentration in B[a]P groups decreased significantlycompared to control group in hippocampus.3. Electron microscope ofhippocampus in B[a]P groups shown that there were lots of blackparticulate matter around neuronal synapse.4. WB result shown that1) theexpression of synaptobrevin protein of hippocampus and cerebral cortex inB[a]P groups had no significant difference compared to control group;2)the expression of SNAP-25protein of hippocampus in0.2mg/kg and2mg/kg B[a]P groups increased significantly, but no significant differencein cerebral cortex compared to control group;3) the expression of syntaxinprotein of cerebral cortex in0.2mg/kg and2mg/kg B[a]P groups decreasedsignificantly, but no significant difference in hippocampus compared tocontrol group;4) the expression of synaptophysin protein of hippocampusin0.2mg/kg and2mg/kg B[a]P groups increased significantly, but nosignificant difference in cerebral cortex compared to control group.5.QPT-PCR result shown decreased expression of Grin1and increasedexpression of Grin2b、Gria1、Gria2、Gabra1、Gabbr1in hippocampus whiledecreased expression of Gria1and increased expression of Grin1、Grin2b、Gria2、Gabra1、Gabbr1in cerebal cotex.Conclution: damage of spatial learning memory in young rat may due toseveral mechanisms:1) decrease of neurotransmitter Glu and GABA in thehippocampus,2) decrease of the calcium ion concentration in hippocampus synapse,3) Neurogranin in hippocampus synapse from B[a]P exposure,4)enhanced expression of SNAP-25、Synaptophysin at the hippocampusand decreased expression of Syntaxin at cerebral cotex,5) decreasedexpression of Grin1and increased expression of Grin2b、Gria1、Gria2、Gabra1、Gabbr1in hippocampus while decreased expression of Gria1andincreased expression of Grin1、Grin2b、Gria2、Gabra1、Gabbr1in cerebalcotex.