The influence of FAAH genetic variation on physiological, cognitive, and neural signatures of fear acquisition and extinction learning in women with PTSD

Endocannabinoid and neuroplasticity-related changes as susceptibility factors in a rat model of posttraumatic stress disorder

Traumatic experiences result in the development of posttraumatic stress disorder (PTSD) in 10-25% of exposed individuals. While human clinical studies suggest that susceptibility is potentially linked to endocannabinoid (eCB) signaling, neurobiological PTSD susceptibility factors are poorly understood. Employing a rat model of contextual conditioned fear, we characterized distinct resilient and susceptible subpopulations based on lasting generalized fear, a core symptom of PTSD. In these groups, we assessed i.) eCB levels by mass spectrometry and ii.) expression variations of eCB system- and iii.) neuroplasticity-related genes by real-time quantitative PCR in the circuitry relevant in trauma-induced changes. Furthermore, employing unsupervised and semi-supervised machine learning based statistical analytical models, we assessed iv.) gene expression patterns with the most robust predictive power regarding PTSD susceptibility. According to our findings, in our model, generalized fear responses occurred with sufficient variability to characterize distinct resilient and susceptible subpopulations. Resilient subjects showed elevated prelimbic and lower ventral hippocampal levels of eCB 2-arachidonoyl-glycerol (2-AG) compared to resilient and non-shocked control subjects. Ventral hippocampal 2-AG content positively correlated with the strength of fear generalization. Furthermore, susceptibility was associated with i.) prefrontal, hippocampal and amygdalar neuronal hypoactivity, ii.) marked decrease in the expression of genes of transcription factors modulating neuroplasticity and iii.) an altered expression pattern of eCB-related genes, including enzymes involved in eCB metabolism. Unsupervised and semi-supervised statistical approaches highlighted that hippocampal gene expression patterns possess strong predictive power regarding susceptibility. Taken together, the marked eCB and neuroplasticity changes in susceptible individuals associated with abnormal activity patterns in the fear circuitry possibly contribute to context coding deficits, resulting in generalized fear.

Exercise and Fear and Safety Learning

Fear conditioning paradigms have been studied for over 100 years and are of great interest to the behavioral and clinical sciences given that several safety learning processes (e.g., extinction learning and recall) are thought to be fundamental to the success of exposure-based therapies for anxiety and related disorders. This chapter provides an overview of preclinical and clinical investigations that examined the effects of exercise on initial fear acquisition, fear extinction learning and consolidation, and return of fear outcomes. This chapter highlights the collective body of evidence suggesting that exercise administered after extinction learning enhances the consolidation and subsequent recall of extinction memories to a greater extent than exercise administered prior to extinction learning. This suggests that the addition of exercise after exposure therapy sessions may improve treatment outcomes for people with anxiety and related disorders. Potential mechanisms are discussed in addition to suggestions for future research to improve our understanding of the effects of exercise on fear conditioning and extinction outcomes.

Predator odor stress reactivity, alcohol drinking and the endocannabinoid system

Post-traumatic stress disorder (PTSD) and alcohol use disorder (AUD) are highly comorbid and individual differences in response to stress suggest resilient and susceptible populations. Using animal models to target neurobiological mechanisms associated with individual variability in stress coping responses and the relationship with subsequent increases in alcohol consumption has important implications for the field of traumatic stress and alcohol disorders. The current review discusses the unique advantages of utilizing predator odor stressor exposure models, specifically using 2,5-dihydro-2,4,5-trimethylthiazoline (TMT) on better understanding PTSD pathophysiology and neurobiological mechanisms associated with stress reactivity and subsequent increases in alcohol drinking. Furthermore, there has been increasing interest regarding the role of the endocannabinoid system in modulating behavioral responses to stress with an emphasis on stress coping and individual differences in stress-susceptibility. Therefore, the current review focuses on the topic of endocannabinoid modulation of stress reactive behaviors during and after exposure to a predator odor stressor, with implications on modulating distinctly different behavioral coping strategies.

Decoding context memories for threat in large-scale neural networks

Humans are often tasked with determining the degree to which a given situation poses threat. Salient cues present during prior events help bring online memories for context, which plays an informative role in this process. However, it is relatively unknown whether and how individuals use features of the environment to retrieve context memories for threat, enabling accurate inferences about the current level of danger/threat (i.e. retrieve appropriate memory) when there is a degree of ambiguity surrounding the present context. We leveraged computational neuroscience approaches (i.e. independent component analysis and multivariate pattern analyses) to decode large-scale neural network activity patterns engaged during learning and inferring threat context during a novel functional magnetic resonance imaging task. Here, we report that individuals accurately infer threat contexts under ambiguous conditions through neural reinstatement of large-scale network activity patterns (specifically striatum, salience, and frontoparietal networks) that track the signal value of environmental cues, which, in turn, allows reinstatement of a mental representation, primarily within a ventral visual network, of the previously learned threat context. These results provide novel insight into distinct, but overlapping, neural mechanisms by which individuals may utilize prior learning to effectively make decisions about ambiguous threat-related contexts as they navigate the environment.

FAAH rs324420 Polymorphism: Biological Pathways, Impact on Elite Athletic Performance and Insights for Sport Medicine

Gene variation linked to physiological functions is recognised to affect elite athletic performance by modulating training and competition-enabling behaviour. The fatty acid amide hydrolase (FAAH) has been investigated as a good candidate for drug targeting, and recently, its single-nucleotide polymorphism (SNP) rs324420 was reported to be associated with athletic performance. Given the implications, the biological pathways of this genetic polymorphism linked to elite athletic performance, considering sport type, psychological traits and sports injuries, need to be dissected. Thus, a narrative review of the literature concerning the biological mechanisms of this SNP was undertaken. In addition to its role in athletic performance, FAAH rs324420 is also involved in important mechanisms underlying human psychopathologies, including substance abuse and neural dysfunctions. However, cumulative evidence concerning the C385A variant is inconsistent. Therefore, validation studies considering homogeneous sports modalities are required to better define the role of this SNP in elite athletic performance and its impact on stress coping, pain regulation and inflammation control.

Assessing and Modelling of Post-Traumatic Stress Disorder Using Molecular and Functional Biomarkers

Post-traumatic stress disorder (PTSD) is a complex psychological disorder that develops following exposure to traumatic events. PTSD is influenced by catalytic factors such as dysregulated hypothalamic-pituitary-adrenal (HPA) axis, neurotransmitter imbalances, and oxidative stress. Genetic variations may act as important catalysts, impacting neurochemical signaling, synaptic plasticity, and stress response systems. Understanding the intricate gene networks and their interactions is vital for comprehending the underlying mechanisms of PTSD. Focusing on the catalytic factors of PTSD is essential because they provide valuable insights into the underlying mechanisms of the disorder. By understanding these factors and their interplay, researchers may uncover potential targets for interventions and therapies, leading to more effective and personalized treatments for individuals with PTSD. The aforementioned gene networks, composed of specific genes associated with the disorder, provide a comprehensive view of the molecular pathways and regulatory mechanisms involved in PTSD. Through this study valuable insights into the disorder's underlying mechanisms and opening avenues for effective treatments, personalized interventions, and the development of biomarkers for early detection and monitoring are provided.

Challenges and considerations for treating PTSD with medicinal cannabis: the Australian clinician's perspective

INTRODUCTION

Preclinical and experimental research have provided promising evidence that medicinal cannabis may be efficacious in the treatment of posttraumatic stress disorder (PTSD). However, implementation of medicinal cannabis into routine clinical therapies may not be straightforward.

AREAS COVERED

In this review, we describe some of the clinical, practical, and safety challenges that must be addressed for cannabis-based treatment of PTSD to be feasible in a real-world setting. These issues are especially prevalent if medicinal cannabis is to be combined with trauma-focused psychotherapy.

EXPERT OPINION

Future consideration of the clinical and practical considerations of cannabis use in PTSD therapy will be essential to both the efficacy and safety of the treatment protocols that are being developed. These issues include dose timing and titration, potential for addiction, product formulation, windows of intervention, and route of administration. In particular, exposure therapy for PTSD involves recall of intense emotions, and the interaction between cannabis use and reliving of trauma memories must be explored in terms of patient safety and impact on therapeutic outcomes.

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.

Fatty acid amide hydrolase C385A polymorphism affects susceptibility to various diseases

The endocannabinoid (eCB) system is an important neuromodulatory system with its extensive network of receptors throughout the human body that has complex actions in the nervous system, immune system, and all of the body's other organs. Fatty acid amide hydrolase (FAAH) is an important membrane-bound homodimeric degrading enzyme that controls the biological activity of N-arachidonoylethanolamide (AEA) in the eCB system and other relevant bioactive lipids. It has been shown that several single nucleotide polymorphisms (SNPs) of FAAH are associated with various phenotypes and diseases including cardiovascular, endocrine, drug abuse, and neuropsychiatric disorders. A common functional and most studied polymorphism of this gene is C385A (rs324420), which results in the replacement of a conserved proline to threonine in the FAAH enzyme structure, leads to a reduction of the activity and expression of FAAH, compromises the inactivation of AEA and causes higher synaptic concentrations of AEA that can be associated with several various phenotypes. The focus of this review is on evidence-based studies on the associations of the FAAH C385A polymorphism and the various diseases or traits. Although there was variability in the results of these reports, the overall consensus is that the FAAH C385A genotype can affect susceptibility to some multifactorial disorders and can be considered a potential therapeutic target.

Enhancing exposure therapy for posttraumatic stress disorder (PTSD): a randomized clinical trial of virtual reality and imaginal exposure with a cognitive enhancer

Posttraumatic stress disorder (PTSD) is a significant public health issue. Yet, there are limited treatment options and no data to suggest which treatment will work for whom. We tested the efficacy of virtual reality exposure (VRE) or prolonged imaginal exposure (PE), augmented with D-cycloserine (DCS) for combat-related PTSD. As an exploratory aim, we examined whether brain-derived neurotrophic factor (BDNF) and fatty acid amide hydrolase (FAAH) moderated treatment response. Military personnel with PTSD (n = 192) were recruited into a multisite double-blind randomized controlled trial to receive nine weeks of VRE or PE, with DCS or placebo. Primary outcome was the improvement in symptom severity. Randomization was stratified by comorbid depression (MDD) and site. Participants in both VRE and PE showed similar meaningful clinical improvement with no difference between the treatment groups. A significant interaction (p = 0.45) suggested VRE was more effective for depressed participants (CAPS difference M = 3.51 [95% CI 1.17-5.86], p = 0.004, ES = 0.14) while PE was more effective for nondepressed participants (M = -8.87 [95% CI -11.33 to -6.40], p < 0.001, ES = -0.44). The main effect of DCS vs. placebo was not significant. Augmentation by MDD interaction (p = 0.073) suggested that depressed participants improved more on placebo (M = -8.43 [95% CI -10.98 to -5.88], p < 0.001, ES = -0.42); DCS and placebo were equally effective for nondepressed participants. There was an apparent moderating effect of BDNF Val66Met polymorphism on DCS augmentation (ES = 0.67). Met66 allele carriers improved more on DCS (ES = -0.25). FAAH 385 A carriers improved more than non-carriers (ES = 0.33), particularly those with MDD (ES = 0.62). This study provides a step toward precision therapeutics for PTSD by demonstrating that comorbid MDD and genetic markers may help guide treatment selection.ClinicalTrials.gov Identifier: NCT01352637.