Effect Of Chronic Psychological Stress On The Behaviors, Immunological Function And NPY In Mice

Objective:This study adopted immobilization stress as chronic psychological stress model in order to observe the effect of chronic psychological stress on change of mood and behaviors,and function of learning,and function of memory and recognition,and immunological function,and CD4,and CD8,and IFN-γ, and IL-4,and neuropeptide Y in mice.It is very important that the uses of medical cure and intervention in sub-health, and increase the structure of human being.Methods:50 BALB/c mice were randomly divided into control group and immobilization stress group(n=25 in each group).The mice mode of stress was made by restraint for 6 hours per day,15 days running.Open-field,Morris water maze and suspend tail test were performed on change of mood and behaviors,and function of learning,and function of memory and recognition in mice.The thymus index and spleen index,the weight of mesenteric lymphocyte node,the number of small intestinal PP node were measured.The content CD4 and CD8,and CD4/CD8 are determined by using flow cytometry.ELISA was employed to measure levels of interferon-γ(IFN-γ) and interleukine(IL-4).RIA was employed to measure levels of neuropeptid- e Y(NPY) in brain.Results: Compared with the control group, restrained mice had relatively longer latency time,the exploring behavior was decreased,and times of defecation was increased. In hidden-platform training of Morris water maze,the mean escape latency of the mice in the chronic restraint groups were longer than that of the control mice.In spatial probe tests,the average percentages of the swimming time in the platform quadrant in the restraint group mice were less than those in the control group.These result show that chronic psychological stress may result in anxiety,depression ,impairs the congnitive function in mice.In suspend tail test,restrained mice had relatively longer staying times.These finding suggest that chronic psychological stress could induce depression.Chronic stress significantly suppressed body weight gain.Spleen index ,the weight of mesenteric lymphocyte node,the number of small intestinal PP node decreased significantly after chronic psychological stress,whereas Thymus index did not change significantly.Chronic stress significantly decreased levels of IFN-γand CD4,and CD4/CD8.These result indicated that chronic psychological stress could aggravate the suppression of immunity in mice.Neuropeptide Y expressions in brain markedly increased in chronic psychological stress. It suggests that NPY is viewed as stress molecular and participate the process of psychological stress.Staying time observed was positively correlated with the latency time and times of defecation,and negatively correlated with times of crossing. These finding imply that cognitive function and exploring behavior and tension may be related with depression and disappointed. Moreover,canonical correlation analysis results showed that latency time and times of defecation observed were positively correlated with the mean escape latency of the mice and levels of IFN-γ,and negatively correlated with the average percentages of the swimming time in the platform quadrant.These observations suggest that mood and cognitive function not only may be related with impairs the function of learning and memory,but also may be related with the suppression of immunity.Conclusion: It was showed that chronic psychological stress could result in anxiety and depression,and suppression of learning and memory,and cognitive changes.Chronic pschologic- al stress could suppress the weight and immunological function.It suggests that chronic ps- ychological stress could induce aggravation the body's natural resistance to environment and result in disease.Chronic psychological stress may induce the changes of NPY which imply that NPY could manuplate the endotrine ,mood and behavior. Chronic psychological stress may induce the change of mood and cognitive function could correlated with impairs the function of learning and memory,the suppression of immunity.these results show that psychological stress is the process of many factors are coeffected.