Effects Of Early Maternal Separation On The Learning And Memory In Rats And Its Neuro-biological Mechanisms

A lot of evidence suggests the importance of early life stress(ELS) in altering both behavioral and several biological parameters underlying pathological changes in adulthood. Early life stress is thought to contribute to many behavioral phenotypes relevant to psychiatric disorders, including major depression, substance use disorder, posttraumatic stress disorder, cognitive deficit, children attention deficit and schizophrenia, but the precise mechanisms underlying this link are poorly understood. The recently studies focus mostly on hypothalamic-pituitary-adrenocortical by using few subjects because of the ethical constraint and technological restriction. Early maternal separation was one of models of adverse early life stress. Mothers form a functional unit with their offspring. It is obvious that during pregnancy the connection is so close that any effect, like stressors, influences both the mother and the pups. Stress during ELS has a wide variety of negative effects in both human and animal offspring.Hippocampal formation is one of the encephalic regions studied by scholars with chemistrical anatomy. Hippocampus(HPC) is acknowledged the learning and studying structure in the brain. There is overwhelming evidence from animal and human studies that the hippocampus is critical to episodic memory. Accordingly, f MRI studies show that the HPC is involved in remembering personal experiences and the order in which they occurred on an autobiographical timeline.Objectives: Animal studies suggest that maternal separation, a widely used paradigm to study the effects of early life adversity, exerts a profound and life-long impact on both brain and behavior. Because we have little understanding about how the HPC contribute to duration memory, The purpose of this paper was to explore the effects of maternal separation on the learning and memory in rats and explore its possible neuro-biological mechanisms.Methods: The neonatal rats 7 days after birth were randomly divided into normal control group(Con), partial maternal separation group(PMS) and complete maternal separation group(CMS). To observe the effects of maternal separation on the learning and memory of adult rats by using Morris water maze, to show the damage of neurons in hippocampus CA1 area by Nissl staining and detect the malondialdehyde(MDA) and superoxide dismutase(SOD) in hippocampus.Results: The escape latent period of PMS rats was longer than that in Con group on third day(P<0.05), the times of crossing platform, the swimming time in the platform area, MDA and SOD had no difference(P>0.05); The escape latent period of CMS rats was longer than that in Con group(P<0.05), the times of crossing platform and the swimming time in the platform area were reduced(P<0.05) compared with Con group and PMS group, the damage of neurons in CA1 area was aggravated, Compared with Con group, MDA was increased(P<0.05)and the SOD was reduced(P<0.05).Conclusions: With the deepening of maternal separation, excessive accumulation of oxygen freely radical in early maternal separation rats brain lead to neurons damage of hippocampus, which may be one of the neurobiological mechanisms of the reduction of learning and memory in rat adulthood. The degree of maternal separation is deeper, the learning and memory of adult rats decreased more, which may be the result from the neuron damage of the hippocampus CA1 area caused by excessive accumulation of oxygen free radical in rat brain.