| Biphenol A(BPA)has long been identified as a typical environmental endocrine disruptor.Its chemical structure is similar to that of diethylstilbestrol,and it has weak estrogen,anti-estrogen and anti-androgen effects.Early laboratory studies have found that BPA exposure can affect social behavior,including play,social inquiry,mating and aggression.The Nucleus accumbens(NAc)is an important part of the midbrain limbic dopamine system and plays an important role in motivation,reward and attention.Dopamine(DA)is a catecholamines neurotransmitter,not only involved in sleep regulation,endocrine regulation and regulation of food intake and other basic physiological functions,but also plays an important role in higher brain functions,such as: reinforcement,reward,movement control,cognitive control and motivation.Some studies have shown that prenatal BPA exposure affects the morphological structure of synapses in the midbrain dopamine system and also affects synaptic functional plasticity,while synaptic plasticity in the central nervous system plays an important role in the study of emotion and behavioral motivation.The effects of BPA on social behavior have been reported,but little research has been done on the effects of BPA on synaptic plasticity in brain regions associated with social behavior,such as NAc.This study first investigated the effect of different doses of BPA on long-term potentiation(LTP)of NAc in adolescence.Androgen receptor antagonist(Flutamide,Flu),estrogen receptor antagonist(ICI 182 780,ICI)and estrogen-related estrogen receptor antagonist(4-hydroxytamoxifen,Tam)were then pretreated to explore whether BPA affects the NAc region LTP through the sex hormone receptor.Then,the regulation of LTP in NAc region by different dose of DA was investigated.Finally,the co-treatment of BPA and DA was conducted to explore whether BPA affects the regulatory effect of DA on LTP in NAc region.Methods: This experiment using electrophysiological techniques to record in vitro slices of NAc area field excitatory postsnaptic potential(field Excitatory Postsnaptic potential,fEPSP)and LTP.Experiments in puberty male first 0.04,0.4 mg/kg/day exposure to BPA in the body of 10 days(3 weeks mice adapt to gastric infections to 10 days after 1 week)to explore the adolescence of BPA in the body of the exposed area of NAc LTP,then with 4 ～ 6 weeks of ICR male mice with acute exposure to 10 nM,100 nM,1 μM,10 μM and 100 μM BPA,different sex hormone receptor inhibitor and different doses of DA acute exposure to the effects of BPA on NAc area LTP mechanism.Firstly,the brains of each treated mouse were taken from their severed heads rapidly,and a 300 μm sagittal brain slices were prepared by using the leica vibration section mechanism,and then placed in an Artificial Cerebrospinal fluid(ACSF)incubation cup continuously fed with a mixture of 95 % oxygen and 5 % carbon dioxide.Record when moving brain slice to record slot,micro manipulation of the instrument is used to change the concentric circles stimulating electrode on the edge of the prefrontal cortex and the nucleus accumbens,the stimulus from prefrontal cortical excitability of neurons,glass recording electrodes placed in the lower part,after of the stimulating electrode recording medium spines neurons of potential changes,will be treated as different slices of continued to contain picrotoxin(100 μM)ACSF perfusion,20 min after giving drugs slices,stimulate the basis of 0.05 Hz after being fEPSP stability,The input-output curves(I/0 curves)were measured by gradually increasing the stimulus intensity(0.01 ～ 0.1 mA).Stable fEPSP at least 10 min was recorded with the stimulus intensity as 50 % ～ 60 % of the maximum response as the baseline.After the baseline recording,3 series of 100 Hz High frequency stimulation(HFS)were given to the brain slices and then returned to the basic stimulation for another 60 min.Finally,pClamp10.3 software was used to measure the slope value of fEPSP,and the average ratio of the slope value of fEPSP per minute in 0 ～ 60 min after HFS to the slope value of fEPSP in 10 min before HFS was calculated as the amplitude of LTP.The experimental data were expressed as mean ± standard error(M ± SE),and one-way ANOVA and two-tailed t test were conducted.Results: 1.After 10 days of body exposure to different doses of BPA in adolescence(10 days after ingestion by gavage in 3-week-old mice),it was found that 0.04 mg/kg/day significantly enhanced the maintenance of LTP(236.8 ± 25.1 %,34.8 % higher than the control group,P < 0.05),while 0.4 mg/kg/day significantly enhanced the maintenance of LTP,suggesting that chronic exposure to BPA could affect LTP in NAc region.2.Different doses of BPA acute treatment of puberty in vitro slices NAc area(pre start recording after incubation for 30 min and continuous dosing),found 100 nM BPA significantly enhanced LTP maintenance(320.1 ± 26.0 %,higher than the control group 128.3 %,P < 0.001),and 100 μM BPA showed inhibition effect to LTP maintain(101.0 ± 12.7 %,90.8 % lower than the control group,P < 0.01),shows the effects of BPA acute treatment of NAc area LTP has a dose dependent effect.3.The enhanced effect of 100 nM BPA on LTP was inhibited by estrogen receptor blockers ICI 182 780,estrogen-related gamma-blockers Tamoxifen,and androgen receptor blockers Flutamide.The mean values of LTP recorded within 60 min after HFS were 166.5 ± 17.1 %(n=6,153.6 %(P < 0.001),and 208.4 ± 25.1 %(n=6,P < 0.001),respectively.The reduction was 111.7 %(P < 0.01)and 175.6 ± 7.8 %(n=6,144.5 %,P < 0.001).Pretreatment with ICI 182 780,an estrogen-receptor blocker,could not eliminate the inhibitory effect of 100 μM on LTP(119.2 ± 15.0 %,n=6).However,treatment with Tamoxifen,an estrogen-related beta-blocker,and Flutamide,an androgen-receptor blocker,could eliminate the inhibitory effect of 100 μM BPA on LTP.The mean value of LTP recorded within 60 min after HFS was 152.0 ± 17.2 %(n=6,50.9 % higher than that of the 100 μM BPA group,P < 0.05)and 153.7 ± 9.6 %(n=6,52.7 % higher than that of the 100 μM BPA group,P < 0.05).The results showed that estrogen-related receptors and androgen receptors not only mediated the rapid enhancement of LTP in NAc region by low dose BPA,but also mediated the rapid inhibition of LTP by high dose BPA.Estrogen receptor mediated only the rapid enhancement of LTP by low dose BPA.4.After the acute treatment of nucleus accumbens brain slices with different concentrations of DA(recording and continuous administration after pre-incubation for 30 min),it was found that 100 nM DA significantly enhanced the maintenance of LTP(291.3 ± 40.1 %,120.7 % higher than the control group,P < 0.001),while 10 μM DA showed an inhibitory effect on the maintenance of LTP,but did not reach a significant level.When BPA at 100 nM and BPA at 100 nM DA were treated together to eliminate BPA,or when DA was treated alone,the promoting effect of LTP in the NAc region was(192.2 ± 15.4 %,n=5),which was 127.9 % lower than that in the 100 nM BPA group(P < 0.01).It was 99.1 % lower than that of the 100 nM DA group(P < 0.05).The results showed that the regulation effect of DA on LTP in NAc region was inverted "U" dose effect,and BPA at 100 nM could antagonize the promotion effect of 100 nM DA on LTP in NAc region.Conclusions: the research results show that adolescent BPA exposure can affect male mice in vivo NAc LTP,adolescence in vitro slices of acute BPA exposure to adolescent male mice of the dual role of the LTP of NAc area has a dose dependent on low doses of BPA rapid enhancement of LTP might be through androgen receptors,estrogen-related receptor gamma and estrogen receptor mediated;The rapid inhibition of high dose BPA on LTP may be mediated by androgen receptor and estrogen-related receptor gamma.At the same time,the regulatory effect of DA on LTP in NAc region presented an inverted "U" dose effect relationship,and the promotion of BPA at 100 nM in LTP antagonized the promotion of LTP in NAc region by 100 nM DA. |
PDF Full Text Request