Acute And Chronic Stress On Spontaneous Behavior And Spatial Learning And Memory Function And Its Mechanism

This study using animal model of single-factor acute stress (foot shock) and multivariate chronic unpredictable stress (crowding, cold/hot stimulation, flat noise, hathpace, foot shock, 28days), we examined the spontaneous behavior and the changes of spatial learning memory ability in mice, and the changes of the expression of c-fos in the brain. This study aims to investigate the effects of acute and chronic stress on the spontaneous behavior and ability of spatial learning-memory in mice and its mechanism. In the present study, we examined the spontaneous behavior of mice in new environment using open field test, and the ability of spatial learning memory of mice using Morris water maze; The corticosterone levels in blood serum of mice were measured using ELISA. the morphologic changes in hippocampus (HP),prefrontal cortex (PFC) and Hypothalamic paraventricular nucleus (PVN) of brain were observed using HE dye, and the expression of c-fos in HP,PFC and PVN of mice brain were examined using immunohistochemical method.The results of this study are as follows:1. After acute stress, compared with the control group mice, the square crossing, rearing and defecation of the stress mice were remarkably decreased, and the central cell residence time was significantly increased; after chronic stress, compared with the control group mice, the square crossing, rearing and grooming of the stress mice were remarkably decreased, the central cell residence time and defecation were significantly increased.2. After acute stress, compared with the control group mice, the escape latency to find platform of the stress group mice were markedly decreased, and in the space exploration test, the resident time in target quadrant remarkable increased in the stress group mice. After the chronic stress, compared with the control group mice, the escape latency to find platform of the stress group mice were significantly increased, and in the space exploration test, the swimming time in target quadrant remarkably decreased.3. After acute and chronic stress, compared with the control group mice, the corticosterone levels of the stress group were remarkably increased, and that the corticosterone levels in acute stress mice the increased was stronger.4. After acute stress, compared with the control group mice, there was no remarkable change in the neuron morphology of the stress group mice. After chronic stress, compared with the control group mice, the number of neurons in HP,PFC and hypothalamic PVN of the stress group mice brain were observably decreased, and cells shrivel and degeneration in theirs, showed varying degrees of damage. 5. After acute stress, compared with the control group mice, the number of positive cells in HP,PFC and hypothalamic PVN of the stress group mice brain were remarkably increased, and the average target gray value was significantly decreased. After chronic stress, compared with the control group mice, the number of positive cells in HP,PFC and hypothalamic PVN of the stress group mice brain were remarkably decreased, and the average target gray value was remarkably increased.Conclusion:1. The acute and chronic stress different treatments reduced the spontaneous behavior of mice in open field test, and it is more evident under conditions of chronic stress.2. The acute stress treatments can prominently enhance the spatial learning-memory ability of mice; and the chronic stress can significantly damage the spatial learning-memory ability of mice.3. The acute stress treatments has no significant effect on neuronal morphology of mice; and the chronic stress cause obvious morphological changes of neurons in HP,PFC and hypothalamic PVN of mice brain.4. The acute stress treatments cause obvious increase of c-fos expression in HP,PFC and hypothalamic PVN of mice brain. The chronic stress induce obvious reduction of c-fos expression in HP,PFC and hypothalamic PVN of mice brain.In the present study, the results suggested that the decrease of the spontaneous behavior and the increase of the spatial learning-memory ability of mice caused by acute stress, and it may be related to the rapid rise of the serum corticosterone and a large number of c-fos expression in HP,PFC and hypothalamic PVN of mice brain. The spontaneous behavioral inhibition and the spatial learning and memory impairment caused by chronic stress may be related to the damage of HP,PFC and hypothalamic PVN neurons in long-time high level corticosterone and the obvious reduction of c-fos expression.