Research On The Effects Of Maternal Separation On Hippocampal Synaptic Plasticity In Neonatal Period

Background and purposes Related studies have shown that maternal separation as early life stress events may affect their learning and memory, cognitive ability.Hippocampus is closely related to the function such as brain emotion, cognition and learning, which is the important cause of maternal and infant behavior change after separation. At the same time, because the hippocampus contains a lot of messenger receptors(e.g., glucocorticoid receptors), become a target of the role of stress hormones, so the hippocampus are easily damaged during stress and plasticity change. Synaptic plasticity is the synapse’s ability to respond to internal and external environmental changes, which is the neurobiology of learning and memory.Synaptic plasticity refers to neurons and synapses parts of certain proteins, including nerve growth associated protein(GAP-43) and synaptic(P38 lightning). GAP-43, involve in the growth of axon endings and synaptic structure reconstruction. What’s more, P38 lightning participate in cell vomiting, cell vomit process and realize the Ca2+ dependence of neurotransmitter release. So it will be nerve growth associated protein and synapses as a symbol of synaptic plasticity response protein.At present, although there are a lot of research on the effects of maternal separation of learning and memory, however, the research which involves the maternal separation on synaptic plasticity change caused by the disorder of learning and memory is very limited, and whether could maternal separation caused the influences of synaptic plasticity through the GAP-43 and P38 is unclear. So this experiment observed hippocampus cell morphology structure and quantity change by setting up maternal separation in the rat model and HE staining, combined with immunohistochemical method to detect related synaptic plasticity protein of rat hippocampal structure after maternal separation: the expression of GAP-43 and P38 lightning level change, discusses the influence of maternal separation on hippocampal synaptic plasticity, analyze the possible mechanisms that maternal separation affects the learning and memory.Methods Selecting 16 new healthy Wistar rats, the baby mice were randomly divided into the separate group and the control group, 8 cases of each group. Separate groups were isolated from 2 days after the birth. This process has lasted for 3 hours in total from 9:00 a.m. to 12:00 a.m. every morning, and then gives these rats up to let them get together with mother. Control group always cage with mother without any processing. Separation group and control group rats were beheaded and take its brain in 22 d after birth as coronary paraffin section after drawing. HE staining has been used to observe hippocampus and dentate gyrus cell morphological changes under light, plan the number of nerve cells. Immunohistochemical method(immunohistochemistry, IHC) has been used to test the expression level of GAP-43 and P38 lightning in hippocampus. Image- Pro Plus 6.0 Image analysis system(IPP) were used to analysis Light density of the immuneohistochemical images. Moreover, SPSS17.0 software also has been adopted for statistical analysis.Results1. Maternal separation could disarrange the marshalling sequence of rat hippocampus cells and make them become sparse than before. Otherwise, maternal separation could wither and denature cells, and reduce the quantity of these cells.2. The distribution and expression of GAP-43 and P38 in rat hippocampus: appearance of tan particles could be viewed as a positive judgment standard, the expression of GAP-43 and P38 occur mainly in hippocampal neuronal cytoplasm, cell membrane and the surrounding nerve fibers.3. GAP-43 in the expression of rat hippocampus: Compared the separation group(137.24±25.10) and the control group(179.22±17.36),the diversity has statistical significance(P < 0.05) expression of separate groups GAP-43 in the hippocampus reduced significantly.4. P38 lightning in the expression of rat hippocampus: compared separation group(84.91±33.48) and control group(185.10±18.47), the difference has statistical significance(P<0.05), the expression of separation group P38 lightning in the hippocampus reduced dramatically.Conclusion Maternal separation of life in the early time can cause the decrease in the number of rat hippocampal neurons, the hippocampus nerve injury may be one of the cause of cognitive emotional disorders. The expression of GAP-43 and P38 lightning appeared different degree of reduction, this could influence the rebuilding and plasticity of rat hippocampal’s synaptic structure, associated with abnormal learning and memory of life which caused by early maternal separation.