Effect Of Maternal Separation On Cognitive Function In Rats And Its Mechanism

Objective:Maternal separation(MS)model was used to simulate early life stress(ELS).Morris water maze and a series of experimental methods were used to study the effect of MS on cognitive function in adult rats and its mechanism.To explore the effects of ELS on rat neural development.MS model was used to simulate ELS.Morris water maze and a series of experimental methods were used to study the effect of MS on cognitive function in adult rats and its mechanism.To explore the effects of ELS on rat neural development.Methods:Twelve healthy SD pregnant rats were randomly divided into two groups: maternal separation group(MS group)and blank control group(NMS group),6 rats in each group.In MS group,the mother rats were separated from their offspring for 3 hours every day from the 3rd day after birth until weaning on the 22 nd day after birth.Group NMS did not take any measures.After weaning,24 offspring of male rats were taken from each group and fed to 10 weeks old.The Morris water maze was used to detect the cognitive function related to learning and memory in adult rats of two groups.The myelin tissue of adult rats was observed by luxol fast blue(LFB).NeuN immunofluorescence staining was used to observe the neuronal cells in the dentate gyrus(DG area)of the hippocampus of adult rats.GFAP/Iba-1 immunofluorescence staining was used to observe astrocytes and microglia in the hippocampus of the offspring of the two groups.Western blot was used to detect the contents of nNOS,eNOS,IL-1beta,IL-6,TNF-a,Bax/BCL2,caspase-3 and P53 proteins in the hippocampus of the offspring of the two groups.Ki67/DCX immunofluorescence staining was used to observe the proliferation and differentiation ofneuronal cells in the hippocampal DG region of adult rats.Fluoro-Jade B myelin staining was used to observe denatured neurons in DG region of hippocampus of rats in both groups.One-step TUNEL staining was used to compare the neuronal apoptosis in the hippocampal DG region of adult rats.Reverse transcription-polymerase chain reaction(RT-PCR)was used to detect the changes of nNOS-mRNA in hippocampus of the two groups.Results:Morris water maze results suggest that the MS group rats have cognitive and dysfunction related to learning and memory ability compared with the NMS group rats,and the MS group rats have longer escape latency,shorter target quadrant residence time,and more.The number of crossing platforms was small(P<0.05).LFB staining showed that the myelin sheath became sparse and vacuolized in the MS group compared with the NMS group,and the demyelination was more obvious.There was no significant difference in the number of normal mature neurons in hippocampus DG between MS group and NMS group(P>0.05),but the number of astrocytes and microglia increased(P<0.05).At the same time,the proliferation of neuronal cells decreased,the differentiation slowed down,and the degeneration and apoptosis increased(P<0.05).Compared with NMS group,the expression of nNOS,eNOS and BCL2 in hippocampus was decreased,and the expressions of Bax,3-NT,IL-1? and TNF-? were increased(P<0.05),but IL-6,caspase-3 and There was no significant difference in the expression of P53(P>0.05).RT-PCR results showed that nNOS-mRNA in hippocampus of rats in MS group decreased compared with those in K group(P < 0.05).Conclusion:MS can affect the development of nerve in rats,leading to partial cognitive dysfunction in adult rats.The mechanism may be to reduce the content of nNOS in hippocampus of rats and induce neuroinflammatory reaction in brain tissue,resulting inhippocampal DG neurons.Cell proliferation is reduced,differentiation is slowed,degeneration and apoptosis are increased.