动物造模,应激抑郁动物模型 z-bo 2021-01-12 321

　　Background: Depression is a complex, heterogeneous, and often chronic mental illness. Clinically, depression exhibits different clinical phenotypes and inconsistent responses to current antidepressant treatments. At present, depression is regarded as a multifactorial disease, including environmental factors, social factors, psychological factors and biological factors. Among these causes, psychological stress is one of the most relevant risk factors for psychosis, and exposure to stressful events can trigger depressive episodes. Animal models are of great significance for studying the molecular and cellular mechanisms of different subtypes of depression and the treatment response to antidepressants. It is generally believed that the same stress will only cause psychopathology in a small part of the population, and only patients with obvious symptoms will receive treatment or intervention. Our previous research found that some animals are resilient and can cope with applied pressure, while some are more vulnerable or under pressure and drop to anhedonia and/or despair like a statue. Animals that are not sensitive to stress are also included in the analysis. In order to mimic the development of human depression, animal models should also exclude insensitive animals. An operating standard needs to be established to distinguish those animals that are not sensitive to stress from those that are sensitive to stress. The role of stress in the development of depression has been extensively studied in animals. For example, animal models based on deprivation of maternal love and chronic unpredictable stress exposure are widely used to simulate the stress of early human life and adulthood. The effectiveness of these depression models has been extensively verified. Since patients with depression have experienced stress in their early years and adulthood, the combination of the two can better reflect depression caused by multiple stresses. However, how do animal models of depression mimic the reactions shown by humans? Only stress-sensitive individuals who can develop depression have not been well resolved. Although some studies actually exclude animals that are not sensitive to stress. In addition, different animals, different stresses, and different behavioral test methods may produce different behavioral test readings.

　　 The establishment of operating guidelines for depressive behavior to exclude animals and abnormal stress insensitivity to animal behavior is a general method to improve animal models of depression. The percentile method is a method used in medicine to determine the reference limit. The main advantage of this method is that the reliability of the sample percentile can be without any assumptions about the shape of the population distribution. Determine the percentile in the sample to be the specified population percentage exclusion requirement (generally greater than 5%, less than 15%). However, whether the percentile method can be used to determine the critical value of depressive behavior in animals has not been confirmed. In this study, we first performed latent profile analysis (LPA) to determine whether a large sample of juvenile rats is a latent subgroup using sucrose preference rate and resting time. If it is successful, we have determined a cut-off value for absence and despair based on the percentile method behavior test readings, followed by the correlation analysis of different behavior intensities and the effect of escitalopram treatment.

　　Method: Adult pregnant SD rats, 12-hour light/dark cycle, free eating and drinking, constant temperature (22±2°C) and humidity (50-55%). Newborn male mice at day 0 (PND 0) were randomly divided into one of the following 4 operating modes: only accept maternal deprivation from PND1 to PND14 (MD, N=111), and only accept chronic unforeseen stress from the tenth Weeks (CUS, N = 122), maternal love deprivation ranged from PND1 to PND14, chronic unpredictable stress ranged from tenth to fourteenth weeks (MD + CUS, N = 99), control group (NOR, N = 120). All animals were weaned at 21 PND.

　　 Maternal Love Deprivation (MD): MD is designed in the way described above. In short, cubs are separated from their mothers for 6 hours every day from PND 1 to PND 14 (separation occurs between 9:00-15:00). The cubs are housed in separate cages. At the end of the separation period, the puppies are returned to their mother cage. The temperature in the cub’s cage was maintained at 32°C for the first 5 days and at 30°C in the later period.

　　 Chronic Unpredictable Stress (CUS): CUS is designed in the way described above. Simply put, a 10-week-old rat was exposed to various continuous pressures for 4 weeks: electric shock to the foot for more than 20 seconds (0.6mA, lasting 1s, 10s once). Put it on an elevated open platform for 2h (10*10cm, height 160cm), crowd for 10h (5-6 mice per cage), use wet litter for 15h, fast for 24h, and restrain stress for 2h. In order to establish unpredictability, stressors are randomly distributed at different times every day. Antidepressant treatment: In this study, the widely used antidepressant citalopram (ESC) was dissolved in 0.9% saline (1 mg/ml) before use; intraperitoneal injection, daily (5 mg/kg) ) For each group of 20 depressed rats for 4 consecutive weeks. The control group received normal saline injections. In order to maintain depression-like behavior, the animals were still cused during the antidepressant treatment.

　　 Sucrose Preference Test (SPT): Evaluate the level of pleasure in rats for a sucrose preference test. This test is performed before the start of CUS and before the weekend of each week. The rats were individually placed in a separate cage and adapted to two bottles of solution (containing 1.5% sucrose solution) for 24 hours. In the next 24 hours, replace a bottle of sucrose solution with water. Then, the rats were fasted for 18 hours and then exposed to two pre-weighed solution bottles (1.5% sucrose solution and pure water, each for 1 hour). Switch the position of the bottle. After the test, the weight and water consumption of the sucrose solution were recorded. Sucrose preference is the ratio of sucrose solution consumption to total fluid intake.

　　 Forced Swimming Test (FST): This test was implemented at the beginning and end of CUS and at the end of anti-depression. Two swimming trainings were performed: 15 minutes of pre-training on the first day and 5 minutes of training on the second day. The rat is forced to swim in a glass tank (21 cm in diameter and 46 cm in height) containing 30 cm of water (25°C). Use intelligent video tracking system for video recording. Analyzed the stationary time (a mouse has no activity during the floating time and only keeps its head above the water). Change the water after each test.

　　Result: Distribution of sucrose preference rate and resting time of juvenile rats: The behavior of juvenile SD rats (n=309) was measured by using sucrose, preference test and forced swimming test. Table 1 provides descriptive statistics of sucrose preference rate and immobile time. Both the sucrose preference rate and the resting time do not obey the Gaussian distribution. The β distribution is more suitable for sucrose preference rate, and the gamma distribution is more suitable for the fixed time of treatment of juvenile rats.

　　 The number of behavioral latent classes in juvenile rats: LPA was performed with behavior test indicators as indicator variables. Table 2 reports the fit index of the competitive potential class model. First compare the 4-level and 5-level models, because all the indices recommend that the 4-level model be retained. Although the AIC, BIC, and aBIC of the 5-level model are lower, the average amount of information suggests that the 4-level model is better than the 5-level model. In general, the 5-level model is not necessarily better than the 4-level model. Therefore, a 4-level model is used.

　　 Behavioral characteristics of different types of adult rats: Analysis of variance shows that the sucrose preference rate and immobility time of the 4-level model are significantly different. Rats have the lowest sucrose preference rate at grade 1, followed by grade 4, grade 2, and grade 3. The immobile time level 4 is the longest, followed by level 2, level 1, and level 3. These findings indicate that in untreated adult rats, sucrose preference and resting time can be used to identify potential individual subgroups. The incidence of depression-like and sub-depressive-like behaviors in rats induced by CUS or CUS+MD: The sucrose preference test was conducted on MD, CUS, MD+CUS and control rats. The average sucrose preference rate of MD, CUS, MD+CUS and control rats is not obvious in anhedonia, subhedonia, and anhedonia rats. There are significant differences in the incidence of anhedonia in the four models. The anhedonia of animals in the MD+CUS group was the most obvious. The incidence of subhedonia in the MD+CUS group was significantly lower than that in the MD group and CUS group. There is a significant difference in the incidence of anhedonic inelastic behavior among the four models. The incidence of anhedonic inelastic behavior in MD + CUS rats is the lowest, and there is no significant difference in the average immobility time of rats in all groups. However, the incidence of despair is significantly different in the four types of models.

　　 The effect of escitalopram on depression and subdepressive behaviors: After 4 weeks of treatment, the recovery rates of pleasure-like behaviors in the four groups of animals were significantly different. The recovery rate of pleasure-like behavior in the CuS group was significantly higher than that in the MD and MD+CUS groups. The recovery rate of pleasure-like behavior in MD group was significantly higher than that in MD+CUS group.

　　 Conclusion: The percentile method in this study is suitable for establishing the operational cut-off point of stress-induced depression sensitivity in rats. The significance of this study includes: (1) This study first established three animal models to study the critical value of stress depression; 2) Further research or data analysis excludes sensitive animals, which more accurately reflects the truth of humans Happening. However, only one type of male rat was used in this study. In clinics, women are generally more likely to suffer from depression than men. In addition, there is only a chronic unpredictable stress model and a maternal deprivation model.