Comparative Analysis of Pathobiochemical Changes in Major Depression and Post-Traumatic Stress Disorder

Comparative analysis of available literature data on the pathogenetic neuroendocrine mechanisms of depression and post-traumatic stress disorder (PTSD) is provided in this review to identify their common features and differences. We discuss the multidirectional modifications of the activity of cortical and subcortical structures of the brain, levels of neurotransmitters and their receptors, and functions of the hypothalamic-pituitary-adrenocortical axis in depression and PTSD. The analysis shows that these disorders are examples of opposite failures in the system of adaptive stress response of the body to stressful psychotraumatic events. On this basis, it is concluded that the currently widespread use of similar approaches to treat these disorders is not justified, despite the significant similarity of their anxiety-depressive symptoms; development of differential therapeutic strategies is required.

Acclimatization to Middle Attitude Hypoxia Masks the Symptoms of Experimental Posttraumatic Stress Disorder, but Does Not Affect Its Pathogenetic Mechanisms

The effects of acclimatization to middle attitude hypoxia on the resistance to acute emotional stress were studied on the model of posttraumatic stress disorder in rats. Anxyolitic, but not anxiogenic effect was observed in acclimatized rats. However, acclimatized rats with posttraumatic stress disorder were characterized by hypofunction of the pituitary-adrenocortical axis, which is typical of this pathology, and reduction in corticosterone/dehydroepiandrosterone ratio. At the neuroendocrine level, up-regulation of glucocorticoid receptors and a decrease in the level of corticotropin-releasing hormone in the hippocampus were revealed. The observed modifications of regulatory mechanisms can underlie hypofunction of the pituitary-adrenocortical axis. It was concluded that acclimatization to middle attitude hypoxia masks behavioral symptoms of posttraumatic stress disorder, but does not alter its pathogenetic neuroendocrine mechanisms.

Epigenetic programming of the neuroendocrine stress response by adult life stress

The hypothalamic-pituitary-adrenal (HPA) axis is critically involved in the neuroendocrine regulation of stress adaptation, and the restoration of homeostasis following stress exposure. Dysregulation of this axis is associated with stress-related pathologies like major depressive disorder, post-traumatic stress disorder, panic disorder and chronic anxiety. It has long been understood that stress during early life can have a significant lasting influence on the development of the neuroendocrine system and its neural regulators, partially by modifying epigenetic regulation of gene expression, with implications for health and well-being in later life. Evidence is accumulating that epigenetic plasticity also extends to adulthood, proposing it as a mechanism by which psychological trauma later in life can long-lastingly affect HPA axis function, brain plasticity, neuronal function and behavioural adaptation to neuropsychological stress. Further corroborating this claim is the phenomenon that these epigenetic changes correlate with the behavioural consequences of trauma exposure. Thereby, epigenetic modifications provide a putative molecular mechanism by which the behavioural phenotype and transcriptional/translational potential of genes involved in HPA axis regulation can change drastically in response to environmental challenges, and appear an important target for treatment of stress-related disorders. However, improved insight is required to increase their therapeutic (drug) potential. Here, we provide an overview of the growing body of literature describing the epigenetic modulation of the (primarily neuroendocrine) stress response as a consequence of adult life stress and interpret the implications for, and the challenges involved in applying this knowledge to, the identification and treatment of stress-related psychiatric disorders.

NPY1 Receptor Agonist Modulates Development of Depressive-Like Behavior and Gene Expression in Hypothalamus in SPS Rodent PTSD Model

Delivery of neuropeptide Y (NPY) to the brain by intranasal infusion soon after traumatic stress has shown therapeutic potential, and prevented development of many behavioral and neuroendocrine impairments in the single prolonged stress (SPS) animal model of PTSD. Therefore, we examined whether the Y1R preferring agonist [Leu³¹Pro³⁴]NPY is sufficient to prevent development of SPS induced depressive-like behavioral changes, and hypothalamic gene expression as obtained with intranasal NPY intervention. Male Sprague-Dawely rats were given intranasal infusion of either NPY (150 μg/rat), a low (68 μg /rat), or high (132 μg/rat) dose of [Leu³¹Pro³⁴]NPY or vehicle immediately following the last SPS stressor, left undisturbed for 1 week and then tested for depressive-like behavior together with naïve unstressed controls. Vehicle treated animals had elevated immobility forced swim test (FST) and reduced sucrose preference, which were not observed in animals given NPY or the higher dose of [Leu³¹Pro³⁴]NPY. This dose of [Leu³¹Pro³⁴]NPY, like NPY, also prevented the SPS-elicited induction of CRF mRNA in the mediobasal hypothalamus. However, [Leu³¹Pro³⁴]NPY did not prevent, but rather enhanced, the SPS-triggered induction of GR and FKBP5 mRNA levels in the mediobasal hypothalamus. Thus, [Leu³¹Pro³⁴]NPY may be as effective as NPY and displays therapeutic potential for preventing development of depressive-like behaviors and dysregulation of the CRF/HPA system in PTSD. However, due to its different effects compared to NPY on GR and FKBP5 a broader agonist, such as NPY, may be more desirable.