The Effect Of λ-cyhalothrin On The Function Of Hippocampus By Interfering With Estrogen In Vivo Study In Mice

Background λ-cyhalothrin is a common type II pyrethroid pesticides with low toxicity, high efficiency, low residue. With the pesticide indiscriminately using, the harm of λ-cyhalothrin caused widespread concern. Research has shown that λ-cyhalothrin neurotoxicity based on the effect of Na+ channel neurotoxicity, this mechanism could explain the acute toxicity of λ-cyhalothrin, but cannot explain the long period toxicity, especially the neural developmental toxicity. The early research found exposed to λ-cyhalothrin will influence development of neural behavior, learning and memory of early after birth of mice. Studies have also shown that adolescence exposed to λ-cyhalothrin could impair the development of cognitive function and behavior of female mice, and the damage is more serious than male mice. As known that estrogen has an important role on central nervous system, especially hippocampal development。and function structure, and λ-cyhalothrin with estrogen interference characteristics. λ-cyhalothrin is likely to influence hippocampal neural development by estrogen interference characteristics.Objective To study the effects of postnatal exposure to λ-cyhalothrin on learning and memory and synaptic development by interfering with estrogen.Methods the female ICR mice were random divided into 12 groups, 8 of those were ovariectomized by anesthetization, The last 4 were sham-operation. The drugs were administrated 7 days after OVX. The OVX groups were received λ-cyhalothrin( LCT,3.0μg/g), Estradiol( E2, 10μg/g), Letrozole( Let, 1μg/g), E2+ Let, E2+ LCT, LCT+ Let, E2+ Let+ LCT and DMSO. Sham groups received LCT, Let, LCT+ Let, and DMSO. Intraperitoneal injection was used for 2 days. The research(Morris water maze and open field test) were initiated 24 h later. Another animals received the same treatments and were sacrificed to be made Frozen section for immunofluorescent assay of postsynaptic density protein 95(PSD95) 24 h after the lasting drug.Results In open field test and the Morris water maze test, the space exploration ability and Learning and memory capabilities were declined when mice were treated with OVX(P <0.05); which effects were reversed when supplement E2(P <0.05); the capabilities wre also declined in normal mice when treated with LCT(P <0.05); same results in OVX+E2+LCT vs OVX+E2(P <0.05); however, the capabilities wre rised when OVX mice received LCT(P<0.05). In the Immunohistochemical fluorescence experiment, the expression of PSD95 wre declined when mice were treated with OVX(P <0.05); and the effects were reversed when supplement E2(P <0.05); the expression of PSD95 were inhibited when druged LCT(P <0.05); and LCT may suppress the up-regulation effect of E2 on PSD95 in OVX mice(P <0.05); but, the expression of PSD95 were also increased when treated with LCT in OVX mice(P <0.05). In Thionin staining, the number of neurons were declined in Sham+LCT compared with ham+con in CA1 and CA3(P<0.05); the number were declined also when treated E2+LCT compared with E2 in OVX groups in CA1 and CA3(P<0.05).Conclusions Adolescence exposure to λ-cyhalothrin may damage the development of hippocampal synapse in the brains of mice by interfering with estrogen, and in estrogen deficiency, λ-cyhalothrin may possess estrogen-like effect.