Effect And Potential Mechanism Underlying Developmental Exposure Of Food-Derived Bisphenol A On Svnaptic Transmission And Brain Circuits

Plastic packaging materials are widely used in modern food packaging.In the process of producing plastics,stabilizers,antioxidants and other auxiliary synthetic materials are added,among which the most widely used is an important chemical synthetic monomer bisphenol A(Bisphenol A,BPA).When plastic products are used for a long time or under high temperature,BPA will migrate from food packaging to food or beverage,which will affect food safety and human health.BPA is a well-known endocrine disruptor(Endocine Disrupting Chemicals,EDCs),which interferes with the physiological activities of normal organisms by affecting the endocrine system.This paper mainly aim at studying the effect of BPA on nervous system and its possible mechanism.Objetive:1.To investigate whether BPA exposure during development affects synaptic transmission and the potential mechanism of the effect at the cellular level.To study whether developmental exposure of BPA affects spatial learning and memory and explore the possible mechanism of this phenomenon.By using the technique of virus tracer and immunohistochemistry,this paper investigates whether BPA developmental exposure affects the spatial learning and memory neural circuits,and probes into the type of neurons affected by BPA,which provides evidence for explaining the neurotoxicity of BPA.Methods:1.The effect of BPA on synaptic transmission was studied upon cultured hippocampal pyramidal neurons in vitro.Whole cell patch-clamp technique recorded miniature excitatory postsynaptic current(mEPSC)and miniature inhibitory postsynaptic current(mIPSC),to investigate whether BPA affects synaptic transmission.Immunocytochemistry was adopted to investigate the expression of key marker of excitatory synaptic transmission and inhibitory synaptic transmission in cultured hippocampal pyramidal neurons after BPA exposure.2.Dual-luciferase assay system of GAD65 estrogen receptor element(GAD65-ERE)was constructed to investigate whether BPA affects synaptic transmission through estrogen receptor classic pathway.3.The morphology and number of dendritic spines in CAl and DG regions of hippocampus were observed by Golgi-cox staining;the spatial learning and memory ability of SD rats was detected by Morris water maze test;Western-blot was used to detect the expression of key proteins in hippocampal CA1 nd DG.4.Retrovirus tracer technique was used to investigate whether the neural projections from the upstream brain regions of the hippocampal CAl or DG regions have changed,and immunohistochemical methods were used to further explore which neuronal types of projections are involved in upstream projections.Results:1.The amplitude of mIPSC in cultured hippocampal pyramidal neurons and the content of Surface GABAA receptor on postsynaptic membrane increased significantly upon BPA exposure.2.Both BPA and estrogen could activate the expression of GAD65-ERE,but when co-existance of BPA and estrogen,the activation was inhibited.3.The spatial learning and memory ability of SD rats decreased significantly after bisphonel A developmental exposure,and the density of dendritic spines,especially mature mushroom dendrites,in hippocampal CAl and DG region was reduced.4.After bisphonel A developmental exposure,the protein expression of Arc in hippocampal CAl and DG regions was significantly decreased.5.he retrovirus tracer data of Thyl-Cre transgenic mice showed that the projection of CA3 to CAl in hippocampus was significantly reduced and the projection from Entorhinal cortex(EC)to CAl region in the external projection of hippocampus was also significantly reduced following BPA exposure.The results of immunohistochemistry showed that the decrease of the projection from EC to CAl region mainly manifested on the decrease of projection from excitatory neurons in EC to the projection neurons in CAl region.Conclusion:1.BPA exposure can affect synaptic transmission function,and this effect was estrogen receptor ERa/? dependent.2.BPA developmental exposure decreased spine density in hippocampal of SD rats and reduced spatial learning and memory abilities.3.The direct neural projection of CA3-CAl and EC-CAl were attenuated by BPA developmental exposure,and these decreases of projection were observed in the projection from excitatory neurons of EC and CA3 to projection neurons of CAl.