Propranolol failed to prevent severe stress-induced long-term behavioral changes in male rats

Paeoniflorin exerts anti-PTSD effects in adult rats by modulating hippocampus and amygdala histone acetylation modifications in response to early life stress

Early life stress (ELS) can cause long-term changes by epigenetic factors, especially histone acetylation modification, playing a crucial role, affect normal cognition, mood, and behavior, and increase susceptibility to post-traumatic stress disorder (PTSD) in adulthood. It has been found that paeoniflorin (PF) can cross the blood-brain barrier to exert anti-PTSD effects on adult PTSD rats. However, whether PF can alleviate the harmful effects caused by ELS in adulthood has not yet been reported. Therefore, to explore the relationship between ELS and PTSD susceptibility in adulthood and its mechanism, in this study, SPS was used as a stressor of ELS, and the mathematical tool Z-normalization was employed as an evaluation criterion of behavioral resilience susceptibility. To investigate the regulatory mechanism of PF on histone acetylation in the hippocampus and amygdala of ELS rats in adulthood, using changes in HATs/HDACs as the entry point, meanwhile, the epigenetic marks (H3K9 and H4K12) in the key brain regions of ELS (hippocampus and amygdala) were evaluated, and the effects of PF on behavioral representation and PTSD susceptibility were observed. This study found that ELS lead to a series of PTSD-like behaviors in adulthood and caused imbalance of HATs/HDACs ratio in the hippocampus and amygdala, which confirms that ELS is an important risk factor for the development of PTSD in adulthood. In addition, paeoniflorin may improve ELS-induced PTSD-like behaviors and reduce the susceptibility of ELS rats to develop PTSD in adulthood by modulating the HATs/HDACs ratio in the hippocampus and amygdala.

On making (and turning adaptive to) maladaptive aversive memories in laboratory rodents

Fear conditioning and avoidance tasks usually elicit adaptive aversive memories. Traumatic memories are more intense, generalized, inflexible, and resistant to attenuation via extinction- and reconsolidation-based strategies. Inducing and assessing these dysfunctional, maladaptive features in the laboratory are crucial to interrogating posttraumatic stress disorder's neurobiology and exploring innovative treatments. Here we analyze over 350 studies addressing this question in adult rats and mice. There is a growing interest in modeling several qualitative and quantitative memory changes by exposing already stressed animals to freezing- and avoidance-related tests or using a relatively high aversive training magnitude. Other options combine aversive/fearful tasks with post-acquisition or post-retrieval administration of one or more drugs provoking neurochemical or epigenetic alterations reported in the trauma aftermath. It is potentially instructive to integrate these procedures and incorporate the measurement of autonomic and endocrine parameters. Factors to consider when defining the organismic and procedural variables, partially neglected aspects (sex-dependent differences and recent vs. remote data comparison) and suggestions for future research (identifying reliable individual risk and treatment-response predictors) are discussed.

Challenges in the use of animal models and perspectives for a translational view of stress and psychopathologies

The neurobiology and development of treatments for stress-related neuropsychiatric disorders rely heavily on animal models. However, the complexity of these disorders makes it difficult to model them entirely, so only specific features of human psychopathology are emulated and these models should be used with great caution. Importantly, the effects of stress depend on multiple factors, like duration, context of exposure, and individual variability. Here we present a review on pre-clinical studies of stress-related disorders, especially those developed to model posttraumatic stress disorder, major depression, and anxiety. Animal models provide relevant evidence of the underpinnings of these disorders, as long as face, construct, and predictive validities are fulfilled. The translational challenges faced by scholars include reductionism and anthropomorphic/anthropocentric interpretation of the results instead of a more naturalistic and evolutionary understanding of animal behavior that must be overcome to offer a meaningful model. Other limitations are low statistical power of analysis, poor evaluation of individual variability, sex differences, and possible conflicting effects of stressors depending on specific windows in the lifespan.