Abstract
BackgroundAnimal models are useful tools for verifying the relationship between stress and depression; however, an operational criterion for excluding the resilient animals from the analysis has not been established yet, which hinders the model’s ability to more accurately mimic the scenario in humans.MethodsTo induce depression-like symptoms, rats received maternal deprivation (MD) during PND1–14, and/or chronic unpredictable stress (CUS) exposure. The latent profile analysis (LPA) was used to determine latent subgroups in treatment naive adult rats. The percentile method was used to distinguish sensitive and non-sensitive behaviors in rats.ResultsThe sucrose preference rate of treatment naive adult rats was fit using a Beta distribution, while immobility time was fit using a Gamma distribution. Indexes of behavioral tests revealed the 4-class model as the best fit for treatment naive adult rats. The incidence of stress-resilience in MD rats was significantly higher than that in CUS rats and MD + CUS rats. There was a significantly higher incidence of stress-resilience in CUS rats compared with MD + CUS rats. Recovery rate of anhedonia-like and sub anhedonia-like behaviors in CUS rats was significantly higher than that in MD and MD + CUS rats. There was a significantly higher recovery rate of anhedonia-like behaviors in MD rats compared to MD + CUS rats.ConclusionsThe percentile method is suitable for setting up an operational cutoff to classify depression-like, sub depression-like, and resilient behaviors in rats exposed to MD and CUS.
Highlights
Animal models are useful tools for verifying the relationship between stress and depression; an operational criterion for excluding the resilient animals from the analysis has not been established yet, which hinders the model’s ability to more accurately mimic the scenario in humans
Beta distribution was a better fit for the sucrose preference rate (Shape 1 = 2.53, Shape 2 = 1.08), while Gamma distribution was a better fit for immobility time (Shape = 2.29, Scale = 0.03) tested in treatment native adult rats (Fig. 2)
There was a significant difference in immobility time between any two groups of rats in each model (Table 6). These results suggested that the operational cutoffs in this study are sensitive to discriminating anhedonia-like behavior from the sub anhedonia-like, and anhedoniaresilient behaviors induced by stress
Summary
Animal models are useful tools for verifying the relationship between stress and depression; an operational criterion for excluding the resilient animals from the analysis has not been established yet, which hinders the model’s ability to more accurately mimic the scenario in humans. Methods: To induce depression-like symptoms, rats received maternal deprivation (MD) during PND1–14, and/or chronic unpredictable stress (CUS) exposure. Depression is viewed as a multifactorial disease that encompasses environmental, social, psychological, and biological factors. Among these etiologies, psychological stress is one of the most relevant risk factors for psychopathologies, and the exposure to stressful events powerfully triggers depressive episodes [4]. To mimic the scenario of depression development in humans, animal models should exclude animals not sensitive to stresses.
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