| Backgrounds and aimsEvidence showed that suffering from chronic unpredictable stress during different stages of pregnancy increased the level of cortisol in the fetal. Fetal's exposure to high level of cortisol impaired the organizational structure and Molecular Biology of the brain, which resulted in cognitive and behavioral disorders after their birth. Moreover, this Neurobehavioral effect on the offsprings may even sustained in their whole life. Presently, many research about the effect of prenatal stress on offspring focused on pregnancy period. But little was known about the effect when the mother was exposed to excess stress before pregnancy. In this research, seven day old SD rats, whose mother received CUS in different stages before pregnancy, were used to observe the level of serum cortisol and hippocampus NCAM expression of the offspring so as to study the effect of pre-pregnancy maternal CUS on the level of cortisol in the offsprings and its relationship with the impaired Molecular Biology of the brain.Methods15 rats were randomly selected from the 27 adult child-bearing period female SD rats which performed normal in open field test and sucrose consumption test. Then these 15 rats received 21 days CUS to build stress animal model and the rest 12 rats as normal control group. These CUS model female SD rats were divided into three groups and copulated with healthy male rats in the period of the next day after CUS, 1 week and 2 weeks after CUS respectively. According to the time of copulating, these CUS SD rats were taken as CUS1 group, CUS2 group, CUS3 group; the healthy control SD rats were divided into three groups with 4 of each according to the time of copulating, which were as follows: C1 group, C2 group, C3 group. The offsprings were grouped according to their maternal: Those delivered by the mother rats fertilized 3-5days after the stress were defined as CUS1 offspring group. Those delivered by the mother rats fertilized 10-12 days after stress as CUS2 offspring group while the ones delivered by the mother rats fertilized 17-19 days after stress as CUS3 offspring group. According to the corresponding fertilization time of the CUS mother rats, the rats delivered by mother rats in normal control group were defined as C1, C2, C3 offspring groups. The offsprings lived with their own mother for seven day since they were born. 8 female and 7 male offspring with the same age in days were selected randomly from each group to be tested. These selected offspring were decapitated and hippocampuses were separated, fixed, embedded and formed paraffin section. NCAM of the hippocampus were measured by immunohistochemistry. At the same time, their plasma was collected to test the level of cortisol.Result1. The Independent behavioral assessment of the female rats in the open field testThere were no differences in the total distance, central distance, peripheral distance between the group of 15 CUS female rats and the normal control group of 12 female rats. (P>0.05); while after the CUS, the above three indexes were lower in the CUS groups compared with the normal control groups(P<0.01). All the index in the CUS groups were lower than that before CUS(P<0.01). In sucrose consumption test, no significant difference was noted in the total fluid consumption, sucrose consumption and sucrose preference ratio between each group (P>0.05).Though the sucrose consumption and sucrose preference ratio of CUS groups were much lower compared with that before stress (P<0.01), the total water consumption showed no difference between each group (P>0.05).2. The detection of cortisol concentration in the CUS offspringsThe cortisol concentration in CUS1 offspring group and C1 offspring group were (117.64±30.84)ng/ml and(83.68±36.63)ng/ml respectively. It was higher in CUS1 group compared with that in C1 group(P<0.05);The cortisol concentration in CUS2 offspring group and C2 offspring group were (108.04±30.84)ng/ml and(82.84±28.14)ng/ml respectively. It was higher in CUS2 group compared with that in C2 group(P<0.05); The cortisol concentration in CUS3 offspring group and C3 offspring group were (106.30±30.56)ng/ml and (86.62±28.91)ng/ml respectively. There were no differences between groups(P>0.05).3.The NCAM expression in hippocampus of the offsprings:The AOD of NCAM in CUS1,CUS2 and CUS3 offspring groups were 0.014±0.010,0.072±0.011and 0.218±0.090 respectively. The AOD of NCAM in C1,C2,C3 offspring groups were 0.223±0.069,0.226±0.081and 0.223±0.080 respectively. The NCAM expression was significant lower in CUS1 and CUS2 offspring group compared with that in C1 and C2 group respectively. however, no significant difference was found between CUS3 offspring group and C3 offspring group(P>0.05).Besides, the NCAM expression in CUS1,CUS2 offspring group was significant lower than that in CUS3 group. As for the extent of decrease, the CUS1 offspring group was larger than CUS2 offspring group. The difference of AOD between CUS1, CUS2 and CUS3 was also highly significant (P<0.01)Conclusion1. In the open field test, the Pre-pregnancy rats had decreased activity and curiosity to the environment after CUS, showed depression behavior; the sucrose consumption test showed that, the female rats which experienced CUS had decreased sensitivity and pleasure deficiency. Therefore, this experiment built a successful pre-pregnancy rat's model.2. The cortisol concentration of the 7-day offsprings in CUS1 and CUS2 offspring group was significant higher than that in C1 and C2 control groups respectively, which indicated that fertilization short-term after pre-pregnancy CUS may expose the offsprings to high level of cortisol and thus impaired its brain development.3. Fertilization short-term after pre-pregnancy CUS decreased its offsprings'NCAM expression when they were born. Moreover, the sooner the mother rats fertilized after CUS, the more obvious abnormal of NCAM expression in the offsprings. The cortisol level of the offsprings had a negative correlation with the NCAM expression, which could also result in impairment of the Neurobehavioral development of the offsprings. |
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