Change Of Pyramidal Neurons In Hippocampal CA3 And Corticosterone Levels In Serum Induced By Chronic Stress And Correlated Study In Rat

Background and Objective:Chronic stress is a precipitative cause for many mental and physical disorders,such as recurrent depression and posttraumatic stress disorder(PTSD).Hippocampus,which belongs to limbic system, play a vital role not only in learning, memory,and other psychological activities,but also in regulating negative feedback of hypothalamic-pituitary-adrenal(HPA) axis. Hippocampus has a plastivity, and is liable to damage during chronic exposure to many injurious factors. Investigation of the changes of neuroanatomy and neurochemistry of hippocampus induced by chronic stress for revealing the pathogenesis of stress-related mental disorders. It was reported that tianeptine ,anantidepressant,blocked stress-induced atrophy of CA3 pyramidal neurons.The purpose of this study is to investigate the effects of chronic stress on structure of hippocampal CA3 pyramidal neurons and levels of corticosterone in serum in rat. Meanwhile, the effects of tianeptine and 12 days after the cessation of stress will be explored.Material and Methods:Rats were divided into control group, stress group, stress-tianeptine group and 12 days after cessation stress group. Rats in stress group, stress-tianeptine group and 12 days after cessation stress group were subjected to forced-swimming for four weeks, a 15-minute session a day. Tianeptine was taken orally in stress-tianeptinegroup every before forced-swimming. Cold boil water was taken orally in other groups in order to avoid the difference induced by being taken orally. Using immunoassay and the microplate reader examine corticosterone levels of serum; Using Golgi staining ,we observed structure of rat hippocampal CA3 pyramidal neurons in the four groups.Results:Chronic stress resulted in a reduction in the body weight gain ,and statistical significance was reached on days 14, 21, and 28(p<0.05 or p<0.01), compared with control animal. Stressed rats on day 28 was more reduction of crossing and rearing than on day 7(p<0.01). There were no significant differences in the ccorticosterone levels of serum among four groups.The total length of apical dendrite was significantly shorter in stress group than that in control, stress -tianeptine, and 12 days after cessation stress group(p<0.01). There were no significant differences in the total length of apical dendrite between stress -tianeptine group and control group or 12 days after cessation stress group(p>0.05).The diameter of dendrite shaft of the hippocampal CA3 pyramidal neurons was significantly thicker in the stress and stress -tianeptine group than that in the control group(p<0.01). There were no significant differences in the control and 12 days after cessation stress group(p>0.05). Conclusions:1) It was showed that chronic stress could suppress body weight gain.2) Chronic stress could induce changes of motion.3) Chronic stress (forced-swimming for four weeks) could not induced the change of CORT levels in serum.This might be involved in habituation.4) Chronic stress could damage to hippocampal CA3 pyramidalneurons.5) Tianeptine could protect hippocampal damage induced by chronic stress.6) CA3 dendritic atrophy was not permanent but reversed to control levels by 12 days after the cessation of stress.