Changes Of Locomotion, Corticosterone And Brain Corticosterone Receptor In Adult Rats With Early Life Stress

Background and Objective: Plenty of clinical and epidemiological numerical data have revealed that early life stress had important influence on memory, character trait, emotion and dealing with stress affairs and even increase the incidence of mental disease. These numerical data are mainly come from the retrospective study of mental patients. Some researches try to discover the biological relation of early life stress and mental disease. These research provide document which reveal the effects of early life stress on neuroendocrine system.. Early life stress evokes the long-term activation which result in the excess stress reaction. The excess stress reaction increases the synthesis and release of ACTH and corticosterone in blood. These lead to a series of neurobiochemistry change and organic lesion in brain. Various research adopt different kinds of stress and confirm the long-term activation which maybe correlate with the mental disease .But we can not ascertain if early life stress affect emotion by excess stress reaction which result in the damage of limbic system. We conjecture that early life stress active the stress reaction which lead to the high level of release of corticosterone. The high level of corticosterone results in excess stress reaction and affects the development of hippocampus in limbic system. These then lead to damage memory and emotion and increase the incidence of mental disease in the end. Our experiments observe the change of locomotion and corticosterone in peripheral blood and corticosterone receptor of the adult rats after early life stress and try to investigate the possible biological mechanism that early life stress affects the emotional ability. This study will benefit the theory of emotional neurobiology and provide biochemical and molecular basis for diagnose and therapy of emotional disorder.Contents and Methods: This study includes two parts: (1) the change of locomotion and corticosterone in peripheral blood and corticosterone receptor of the adult rats after early life stress (2) the change of locomotion and corticosterone in peripheral blood and corticosterone receptor of the adult rats after chronic stress .Results:1 Effects of early life stress on locomotion and corticosterone in peripheral blood and corticosterone receptor of the adult rats.1.1 Effects of early life stress on locomotion. 1.1.1 Effects of 1h early life stress on locomotion.The total activity time of locomotion was increased (compared with normal control group, P=0.006<0.01, t test) in 2 months old rats after 1h early life stress. The locomotion was not changed in 3 months old rats after 1h early life stress. The total activity time of locomotion was reduced (compared with 2 months old rats, P=0.034<0.05, t test) in 3 months old rats after 1h early life stress. These results reveal that 1h early life stress maybe lead to the increase of emotional behavior which was reduced by the increase of the rat age.1.1.2 Effects of 3h early life stress on locomotion.The total activity time of locomotion was increased (compared with normal control group, P=0.004<0.01, t test) in 2 months old rats after 3h early life stress. The locomotion was not changed in 3 months old rats after 1h early life stress. The total activity time of locomotion was reduced (compared with 2 months old rats, P=0.041<0.05, t test) in 3 months old rats after 3h early life stress. These results reveal that 3h early life stress maybe lead to the increase of emotional behavior which was reduced by the increase of the rat age.1.1.3 Effects of different early life stress on locomotion.The total activity time of locomotion was increased (compared with rats which suffer 1h early life stress, P<0.01, t test) in 2 and 3 months old rats after 3h early life stress; These results reveal that the emotional behavior was increased by the increase of the early life stress.1.2 Effects of early life stress on corticosterone in peripheral blood.1.2.1 Effects of 1h early life stress on corticosterone in peripheral blood.The concentration of corticosterone was increased (compared with normal control group, P=0.014<0.05, t test) in 2 and 3 months old rats after 1h early life stress. The concentration of corticosterone was not changed in 3 months old rats after 1h early life stress. The concentration of corticosterone was reduced (compared with 2 months old rats, P=0.008<0.01, t test) in 3 months old rats after 1h early life stress. These results reveal that 1h early life stress maybe lead to the increase of the concentration of corticosterone which was reduced by the increase of the rat age.1.2.2 Effects of 3h early life stress on corticosterone in peripheral blood. The concentration of corticosterone was increased (compared with normal control group, P P<0.01, t test) in 2 and 3 months old rats after 3h early life stress. The concentration of corticosterone was not changed (compared with 2 months old rats) in 3 months old rats after3h early life stress. These results reveal that 3h early life stress maybe lead to the increase of the concentration of corticosterone which was not changed by the increase of the rat age.1.2.3 Effects of different early life stress on corticosterone in peripheral blood.The concentration of corticosterone was increased (compared with rats which suffer 1h early life stress, P<0.01, t test) in 2 and 3 months old rats after 3h early life stress; These results reveal that the concentration of corticosterone was increased by the increase of the early life stress.1.3 Effects of early life stress on corticosterone receptor in hippocampal CA3 areaPositive cell population (compared with normal control group, P=0.001<0.01, T test) and positive area rate (compared with normal control group, P=0.002<0.01, T test) in hippocampal CA3 area were reduced in 2 months old adult rats after 3h early life stress. Positive cell population and positive area rate were not changed in 3 months old rats after 3h early life stress. Positive cell population and positive area rate were increased (compared with 2 months old rats) in 3 months old rats after 3h early life stress. These results reveal that 3h early life stress maybe lead to the decrease of positive cell population and positive area rate which was reduced by the increase of the rat age.2 Effects of chronic stress on locomotion and corticosterone in peripheral blood and corticosterone receptor of the adult rats which had suffered early life stress2.1 Effects of chronic stress on locomotion of the adult rats which had suffered early life stress2.1.1 Effects of chronic stress on locomotion of the adult rats which had suffered 1h early life stressThe total activity distance of locomotion (compared with rats which suffer chronic stress, P=0.015<0.05, t test) and the total activity time of locomotion (P=0.003<0.01, t test) were increased in adult rats which suffered 1h early life stress and chronic stress. 1h early life stress may more easily result in the increase of the locomotion after chronic stress.2.1.2 Effects of chronic stress on locomotion of the adult rats which had suffered 3h early life stressThe total activity distance of locomotion (compared with rats which suffer chronic stress, P=0.025<0.05, t test), the central activity distance of locomotion(P=0.002<0.01, t test) and the total activity time of locomotion (P=0.002<0.01, t test) were increased in adult rats which suffered 3h early life stress and chronic stress. 3h early life stress may more easily result in the increase of the locomotion after chronic stress.2.1.3 Effects of chronic stress on locomotion of the adult rats which had suffered different early life stressThe total activity distance, the peripheral activity distance and the peripheral activity time of locomotion (compared with rats which suffer 1h early life stress and chronic stress, P<0.01, t test) were increased in adult rats which suffered 3h early life stress and chronic stress. This result reveals that the increase of the locomotion by chronic stress was improved by the increase of early life stress.2.2 Effects of chronic stress on corticosterone in peripheral blood of the adult rats which had suffered early life stressThe concentration of corticosterone (compared with rats which suffer chronic stress, P<0.01, t test) in peripheral blood were increased in adult rats which suffered 1h or 3h early life stress and chronic stress. 1h or 3h early life stress may more easily result in the increase of the concentration of corticosterone in peripheral blood after chronic stress. The concentration of corticosterone (compared with rats which suffer 1h early life stress and chronic stress, P<0.01, t test) were increased in adult rats which suffered 3h early life stress and chronic stress. This result reveals that the increase of the concentration of corticosterone in peripheral blood by chronic stress was improved by the increase of early life stress.2. 3 Effects of chronic stress on corticosterone receptor of the adult rats which had suffered early life stressPositive cell population and positive area rate of corticosterone receptor in hippocampal CA3 area are (compared with rats which suffer chronic stress, P<0.01, t test) were induced in adult rats which suffered 3h early life stress and chronic stress. This result reveals that the decrease of the corticosterone receptor in hippocampal CA3 area by chronic stress was improved by 3h early life stress.Conclusions: 1. Early life stress may result in the increase of the locomotion which has positive relation with the intensity of early life stress and has negative relation with the increase of the rat age.2. Early life stress may result in the increase of the concentration of corticosterone in peripheral blood which has positive relation with the intensity of early life stress and has negative relation with the increase of the rat age.3. Early life stress may result in the decrease of the positive cell population of the corticosterone receptor in hippocampal CA3 area which has negative relation with the increase of the rat age.4. Early life stress may more easily result in the increase of the locomotion and the concentration of corticosterone in peripheral blood and the decrease of the positive cell population of the corticosterone receptor in hippocampal CA3 area after chronic stress. This change has positive relation with the intensity of early life stress.These results reveal that early life stress may lead to the increase of the emotional behavior whose mechanism may have relation with these reactions below. Early life stress result in the excess stress reaction of HPA axis which lead to the long-term high level of concentration of corticosterone and the decrease of the positive cell population of the corticosterone receptor in hippocampal CA3 area results in the decrease of negative feedback. The details need to investigate in the future.