| PART Ⅰ EFFECTS OF DI-N-BUTYL PHTHALATE ON COGNITIVE FUNCTION OF OFFSPRING RATS AT DIFFERENT AGES AFTER PERINATAL EXPOSUREObjective: To study the neurotoxicity of di-n-butyl phthalate(DBP)on offspring rats in childhood and adulthood after perinatal exposure,and discuss whether there is still persistent brain damage in adult offspring.Methods: Pregnant SD rats were randomly divided into three DBP treatment groups and one control group,respectively given 50mg/(kg·d)DBP(low-dose treatment group,n=10),200mg/(kg·d)DBP(medium-dose treatment group,n=10),500mg/(kg·d)DBP(high-dose treatment group,n=16)or vehicle only(control group,n=8)by gavage once a day from gestation day6(GD6)to postnatal day23(PND23)consecutively.When offspring rats were at the age of PND21 and PND60: the general effects of DBP on pregnant and offspring rats were observed.Cognitive function of the offspring was evaluated by Morris water maze.Brain activity was recorded with electrocorticography.Morphological changes of the hippocampus were observed via HE staining.Results: Compared to those of control group,the pups in high-dose treatment group were markedly fewer(P<0.05),and pups in the medium-dose treatment group showed lower birth weight(P<0.05).In the water maze test,the escaping latency of young offspring in DBP treatment groups was longer than that of control(P<0.05).The pups in the former groups also spent less time in the target quadrant(P<0.01),and the numbers of crossing the platform were fewer,too(P<0.01);male pups in the medium-dose treatment group showed worse performance in probe test than other groups(P<0.01).During EEG recording,the pups in DBP treatment groups were found to have more delta activity and delta+theta activity(P<0.01),while less theta and alpha activity(P<0.05);likewise,there were more delta+theta activity in pups of medium-dose and high-dose treatment group than those of low-dose treatment group(P<0.05)and control group(P<0.01).HE staining showed that in the medium-dose and high-dose treatment group,the cell number in CA3 and DG region of the hippocampus decreased slightly,and so did the cell density.With regard to the adult offspring,there were no significant differences between DBP treatment groups and control group regarding the escaping latency,time in the target quadrant and numbers of crossing the platform(P>0.05).But compared to those in control group,The female offspring in low-dose treatment group still showed worse performance in the water maze test(P<0.05).During EEG recording,although the adult offspring in DBP treatment groups showed some improvements than younger ones,they were still found to have more delta activity and delta+theta activity(P<0.01),while less theta and alpha activity(P<0.01),compared to those in control group.HE staining showed that no significant differences were found in hippocampal formation or cell number between DBP treatment groups and control group.Conclusion: Those findings indicate that DBP could cause cognitive dysfunction and slower brain rhythms in offspring rats after perinatal exposure.The adult offspring rats in DBP treatment groups showed some improvements than younger offspring;but influence of DBP on brain activity could last to adulthood,and so is the cognitive impairment in offspring rats of low-dose treatment group.Effects of DBP exhibit nonmonotonic dose dependence and some kind of sex discrepancies.The damage was more severe in male offspring rats of the medium-dose treatment group.PART Ⅱ POSSIBLE MECHANISM OF COGNITIVE IMPAIRMENT INDUCED BY DI-N-BUTYL PHTHALATE IN OFFSPRING RATS AFTER PERINATAL EXPOSUREObjective: To explore the possible mechanism of DBP-induced neurotoxicity on offspring rats after perinatal exposure.Methods: Pregnant SD rats were randomly divided into DBP treatment group(n=10)and control group(n=8),respectively given 200mg/(kg·d)DBP or vehicle only by gavage once a day from gestation day6(GD6)to postnatal day23(PND23)consecutively.Then the hippocampus was prepared from PND5,PND21 and PND60 offspring rats.The expression of estrogen receptor β(ERβ),brain-derived neurotrophic factor(BDNF)and neuropeptide Y(NPY)protein in the hippocampus were determined by Western blot analysis.Results: Compared to those of control group,the expression of ERβ,BDNF and NPY was significantly decreased in offspring rats of DBP treatment group(P<0.01);male offspring in DBP treatment group had a greater decrease(P<0.01).In control group,the expression of BDNF and NPY increased as age(P<0.05).However,after DBP treatment,the expression of BDNF and NPY in male offspring in adulthood were even fewer than that in childhood(P<0.05);expression level was similar in female between adulthood and childhood offspring rats.Conclusion: DBP could cause reduction in expression of ERβ,BDNF and NPY in offspring rats after perinatal exposure in a sex-specific manner,which may be the underlying mechanism of cognitive dysfunction and brain damage in offspring rats caused by DBP.The damage was more severe in male offspring rats of DBP treatment group.The influence of DBP on BDNF and NPY expression could last to adulthood. |
PDF Full Text Request