The Effect Of Maternal Pregestational Cus On The Serum CRH And COR, Brain Dopamine And 5-ht Metabolisms And Its Correlation With The Behavior Of Offspring Rats

Backgrounds and aimsThe chronic unpredictable stress (CUS) before or throughout the whole pregnancy impairs neural development of the offspring, as well as their cognition, memory and behavior. Our resent research found out that pregestational CUS increased the COR level of the offspring after birth, and lowered the expression of BDNF, NMDA and NR2B in the hippocampus. However, researches on how maternal CUS affects the HPA axis of the offspring and brings the above neural and behavioral damages remain initial stage. In this research, we established a CUS model using Sprague-Dawley (SD) rats, made them pregnant right after the 21-day stress procedure, detected the CRH and COR levels before pregnancy and after delivery. When the offspring grew into 1-month old, forced swimming test (FST) was carried out, and we detected the serum CRH and COR levels as well as DA and 5-HT metabolisms in the brain to study how maternal pregestational CUS affects the neural development and behavior of the offspring.MethodsAdult female SD rats were divided randomly into two groups: control group (n=10) and CUS group (n=15). When the procedure of CUS finished (24 hours after the last stressor), female rats were housed by pairs with a male for one week for mating, before which blood samples were collected for CRH and COR detection. The day on which sperm was observed in vaginal smears was designated as embryonic day 0 (E0). The day of delivery was designated as postnatal day 0 (PND0), within 6 hours we collected blood samples again for post-delivery CRH and COR tests. When the offspring rats were PND30, they were divided according to their maternal group: offspring of control group (n=40; 20 females in CF group and 20 males in CM group) and offspring of CUS group (n=40; 20 females in CUSF group and 20 males in CUSM group). After forced swimming test, they were killed and blood samples were collected for serum CRH and COR tests, brain tissues from cerebral cortex, hippocampus and midbrain were obtained for the detection of DA and 5-HT metabolisms by HPLC. Results1. After the stress procedure, maternal serum CRH level in CUS group(34.22±5.99) pg/ml was higher than control group(25.27±4.02)pg/ml, (P<0.01). The COR level in CUS group(115.86±11.43)ng/ml was also significantly higher than controls (90.48±10.11) ng/ml, (P<0.01). The post-delivery CRH level in CUS group (42.21±9.28)pg/ml was higher than controls (33.15±4.28)pg/ml, (P<0.05), the post-delivery COR level in CUS group(127.98±13.97) ng/ml was also significantly higher than controls (119.25±14.50) ng/ml, (P<0.05).2. The CRH level was higher in CUSF group (34.31±4.53)pg/ml than CF group (28.24±4.86) pg/ml, the COR level of CUSF group (107.51±18.28)ng/ml also presented a significant increase than the CF group (86.63±16.87)ng/ml; And the CRH level of CUSM group (35.21±5.00)pg/ml was significantly higher than the CM group (27.90±4.20) pg/ml; The COR level of CUSM group (109.04±18.14)ng/ml also presented a significant increase than the CM group (86.15±18.21)ng/ml; All the above differences were highly significant(P<0.01).3. In the forced swimming test, the immobility of CUSF group(18.88±6.29)s was significantly longer than the CF group(8.42±3.37)s. The CUSM group also presented longer immobility (17.44±6.71)s than CM group (8.70±2.70)s. The total activity of CUSF group (280.92±6.29)s was significantly shorter than CF group (291.38±3.37)s, and that of CUSM group (282.36±6.71)s was also shorter than CM group (291.10±2.70)s. All the above differences were highly significant(P<0.01).4. The DA concentration of CUSF and CUSM groups were significantly lower than controls of the same gender in the cerebral cortex, hippocampus and midbrain, while the DA metabolic rates were significantly higher(P<0.05 or P<0.01). In contrast, the 5-HT concentrations were higher in CUSF and CUFM groups than controls of the same gender while the 5-HT metabolic rates were lower in all the above brain regions(P<0.05 or P<0.01). 5. Both the post-stress and post-delivery CRH levels were positively correlated with the COR levels of the same period. The CRH level of the 1-month offspring was positively correlated with both their own COR level and the maternal post-stress CRH level.6. The post-stress maternal CRH and COR levels increased the immobility of the offspring and decreased the total activity during FST. Meanwhile they increased the DA metabolisms and decreased 5-HT metabolisms in all the cerebral cortex, hippocampus and midbrain regions. And the CRH and COR levels of 1-month old offspring were significantly correlated with their performances in the FST, and they were also negatively correlate with DA concentrations and positively correlated with DA metabolisms in cerebral cortex, while in midbrain they were positively correlated with 5-HT concentrations and negatively correlated with 5-HT metabolisms.7. In FST the immobility of 1-month old offspring was positively correlated with the DA metabolisms and negatively correlated with 5-HT metabolisms in all the cerebral cortex, hippocampus and midbrain regions. And the total activity was negatively correlated with the DA metabolisms and positively correlated with 5-HT metabolisms in the above brain regions. The DA concentrations in cerebral cortex and hippocampus were negatively correlated with the immobility and positively correlated with the total activity in FST, while the 5-HT concentrations in cerebral cortex and midbrain were positively correlated with the immobility and negatively correlated with the total activity in FST.Conclusion1. The CRH and COR levels of maternal rats suffering from CUS were significantly higher than control group not only after the CUS procedure but also after delivery, which indicates HPA-axis hyperactivity of CUS maternal rats exists throughout the whole pregnancy.2. The CRH and COR levels of 1-month old offspring were significantly higher than controls and to some extend correlated with the maternal CRH and COR levels, which indicates maternal HPA-axis hyperactivity and imbalance can lead to HPA-axis hyperactivity of the offspring directly or indirectly.3. In the FST carried out when the offspring rats were 1 month old, both female and male offspring from CUS group performed longer immobility and less total activity. According to the correlation among the maternal and offspring CRH and COR levels and their performance in the FST, and the fact that DA and 5-HT metabolic imbalances existing in the offspring central nervous system and significantly correlated with the performance in FST, a conclusion can be drawn that the behavioral disorders of offspring are the consequence of both HPA-axis hyperactivity and the abnormality of DA and 5-HT metabolisms, which indicates CUS shortly before pregnancy can cause brain function insufficiency.