Effects Of Nonylphenol Exposure During Pregnancy And Lactation On LTP And Neurobehavior In Offspring Rats

Objective: Polyoxyethylene nonyl phenyl ether(NPE)is a nonionic surfactant.It was widely used in industrial additives and daily necessities.For example,emulsifying agents,cleaning agents,flotation agents and industrial cleaners to pulp and paper industry,household chemicals,metal surfaces and leather processing.Nonylphenol(NP)is the most predominant degradation product of nonylphenol ethoxylates.With the widespread use of NP and its non-degradable properties,the toxic effects of NP have attracted widespread attention.The neurodevelopmental toxicity is one of the hot spots.Several decades studies suggest that NP exposure at the critical phase of brain development may cause the impairment of learning and memory.However,the direct laboratory evidence to support this view is seldom.The specific mechanism is still not clear.The hippocampus is a central brain region involved in learning and memory.Long-term synaptic plasticity is the basis for learning and memory.BDNF-AKT-mTOR signaling pathway and its downstream protein PSD-95 are closely related to learning and memory.Does NP affect learning and memory ability by interfering with the BDNF-AKT-mTOR signaling pathway and its downstream protein PSD-95? In this study,we examined whether the NP exposure during pregnancy and lactation had an effect on the learning and memory of the pups through the Open field test(OF),the Morris water maze(MWM)and electrophysiological experiments.On this basis,the changes of BDNF-AKT-mTOR signaling pathway and its downstream protein PSD-95 were detected.Thus,we explored the effect of NP exposure during pregnancy and lactationon on the learning and memory of the pups and the possible mechanism.Methods: The pregnant female rats were randomly divided into four groups: 0 mg/kg/day,10 mg/kg/day,50 mg/kg/day and 100 mg/kg/day groups.The pregnant female rats were gavaged with the corresponding concentration of NP.Open field test,Morris water maze,and electrophysiological experiments were performed on PN60 and PN80.Western blot and immunofluorescence were used to detect related proteins on PN80.Results: 1.Effects of NP exposure during pregnancy and lactation on the Open field test in offspring:(1)the rearing frequency: 100 mg/kg group compared to that of the 0 mg/kg group,the difference was statistically significant(P < 0.05);the other two groups were not statistically significant(P > 0.05).(2)All distance: there were no significant differences among the four groups.2.Effects of NP exposure during pregnancy and lactationon on the Morris water maze in offspring.(1)During the first three days of training,10 mg/kg group,50 mg/kg group and 100 mg/kg group all spent more time to hunt for the platform compared to that in the 0 mg/kg group,but the differences were not statistically significant.At the last two days,10 mg/kg group,50 mg/kg group and 100 mg/kg group all spent more time to hunt for the platform compared to that in the 0 mg/kg group,the differences were statistically significant(P < 0.05).(2)In the spatial probe trial: the time in Morris water maze platform quadrant is the same as the first time reach the platform quadrant: 100mg/kg group compared to that of the 0 mg/kg group,the difference was statistically significant(P < 0.05).The other two groups were not statistically significant.The results indicated that platform zone entries were no differences among the four groups.3.Effects of NP exposure during pregnancy and lactation on the Electrophysiology Experiment in offspring: Baseline synaptic transmission suggested by f-EPSP slope and PS amplitude did not differ among the four groups.Then,100 Hz HFS was given in the hippocampal CA3 area of each group to induce(Long-term potentiation)LTP.And record for 30 minutes.As a result,it was found that the f-EPSP slope and the PS amplitude of each group significantly increased after HFS.It was further found that the increase in f-EPSP slope and PS amplitude in each treated group was significantly reduced compared with the 0 mg/kg group(P < 0.05).These data indicated that NP exposure during gestation resulted in damage to LTP in pups.4.Effects of NP exposure during pregnancy and lactation on the BDNF-AKT-mTOR signaling pathway and its downstream protein PSD-95 in offspring.(1)10mg/kg,50mg/kg and 100mg/kg compared to 0mg/kg the fluorescence intensity had decreased,the differences were statistically significant(P < 0.05).(2)The fluorescence intensity of P-AKT gradually decreased with increasing dose.(3)The total amount of AKT among the four groups remained stable.However,the activity of phosphorylated AKT of 100mg/kg group compared to that of the 0 mg/kg group,the difference was statistically significant(P < 0.05),and the other two groups were not statistically significant.(4)The activity of mTOR,P-mTOR,PSD-95 gradually decreased with increasing dose.10mg/kg compared to 0 mg/kg the difference was not statistically significant.However,the difference was statistically significant,whether compared with 100mg/kg and 0mg/kg or 50 mg/kg and 0 mg/kg(P < 0.05).Conclusion: 1.NP exposure during pregnancy and lactation impaired the learning and memory in offspring indicated by Open field,Morris water maze and LTP in vivo.2.Effects of NP exposure during pregnancy and lactation on learning and memory in offspring were related to its interference with BDNF-AKT-mTOR signaling pathway.