The Establishment Of Psychological Stress Rat Model And The Evaluation Of Related Factors

Stress has become an important factor in the development of disease, the establishment of desirable stress model is very important in human stress research. Hypothalamus-pituitary adrenal (HPA) axis is the most important way to the role of psychological stress.The activation of HPA axis may regulate ACTH and cortisol secretion, which affects the behavior related to stress, neuroendocrine-immune activity. This study based on the theory of hypothalamus-pituitary-adrenal axis, established psychological stress rat model and evaluated it by determining the content of ACTH in rat serum,body weight,blood pressure, electrocardiogram, cardiac histopathological in rats, analysed the role of the stress factors in the rat model, which provided sufficient experimental evidence for further clarifying the mechanism of myocardial injury induced by psychological stress in the miRNA.Objective:To explore the establishment of psychological stress rat model and evaluate the significance of related factors.Methods:2 months old male Wistar rats were randomly divided into normal control group, chronic stress group and acute stress group. Giving random stimulation at different times during the day,while forbiding eating and drinking, measuring body weight, blood pressure and electrocardiogram of the experiment rats every 3 days during the experiment. After the stress experimental, blooding from superior vena cava, measuring the level of ACTH by using enzyme-linked immunosorbent assay. Rats were dissected after general anesthesiato, collecting myocardial histopathology and producing mmunohistochemistry specimen, electron microscope specimen in order to observe the changes of myocardial tissue.Results:(1) After a week of stress, rats perfomed behavior of excitement and anxiety in order to avoid stimulating, containing resistance,screaming,increasing Fenqiu,breathing faster, frightening, staring eyes, a high degree of vigilance, etc. After two weeks the behavior of excitement gradually reduced, acting suppression and depression later. Hair was sparse, messy, and dull, showing an air of fatigue, eye lost its luster, body shape was thin, eating reduced, the ability to respond significantly reduced, etc. (2) Body weight of rats after stress were increased in model group and control group, there was no significant difference in weight 6 days ago, form 6th day to 15th day the group differences in weight compared with the control group was statistically significant (P<0.01). weight of model group increased more slowly than that of the control group. (3) There was significant difference (P<0.01) in blood pressure of model group and control group form 6th day to 15th day. systolic blood pressure increased form (113.25±1.91) mmHg to (125.00±3.42) mmHg. and there was no significant differencet in control group before and after the experiment. (4) The concentration of ACTH was significant higher in chronic stress rats than normal control group. Difference between the two groups was significant (P<0.01). (5) The ECG of all rats before stress was normal, after stimulation for 2 weeks, the ECG record of different individuals in stress group showed sinus tachycardia, atrial premature contraction, ventricular arrhythmia, elevation or depression in ST segment and appeared flat or inverted T wave. (6) The mmunohistochemistry in myocardial tissue showed: the arrangement of cell nucleus was regular in normal group, the staining of nuclei and cytoplasm was uniform, there were no brown-yellow granules. Nucleus were disordered in stress group, the cytoplasm was irregular, the number of cells reduced and cell gap increased. the inflammatory cell can be seen in chronic stress group. There was a large number of brown yellow granules around the nucleus and the cytoplasm in stress group. (7) Result of myocardial electron microscopy:Control group:myocardial cell nucleus are oval with prominent nucleoli, euchromatin is plentiful in the nuclei, arrangement of filaments is neat, light and dark of sarcomere is clear, mitochondria is among myofilament and tubules are in the Z line. Acute stress:myocardial cell nucleus are oval, heterochromatin is plentiful in the nuclei, mitochondria increasing and swelling, Cristae is irregularly arranged, some mitochondria show condensation, matrix cavitation. cardiac intercalated disk arrays inordinately, the space of connection structure disappears, showing compact form, myofilament dissolves and fractures. Chronic stress group:myocardial cell nucleus are oval, matrix is slightly dense, mitochondria arranges lengthwise in the muscle, mitochondria increases and swells slightly, Partial cavitation is around individual mitochondria, Sarcomere structure can be identified, light and dark of sarcomere is clear in part, the number of myofilament reduces slightly, intercalated disk position is normal vertically and horizontally.Conclusion:(1) In this study, we established acute and chronic psychological stress model by multiple stress stimulation, during the stress process animals showed a series of changes in behavior and blood pressure, body weight. (2) HPA axis may be activated in stress, reactivity increased. Evaluation of ACTH level of stress model is a better indicator. (3) ECG in stress rat can show the exact myocardial ischemia, arrhythmia. (4) After myocardial stress, the expression of HSP70 in rats increased in order to protect the stress-induced cell damage. (5) Ultrastructure shows that acute and chronic stress can induce myocardial cell injury, but the extent of myocardial injury in acute stress group is heavier, so the establishment of acute stress model is more essential. (6) The animal model of this experimental can be established for general stress disorders, which lays a foundation for the mechanism and function of myocardial injury induced by psychological stress in miRNAs.