Single-prolonged stress induces apoptosis by activating cytochrome C/caspase-9 pathway in a rat model of post-traumatic stress disorder

Mitochondrial dysfunction as a possible trigger of neuroinflammation at post-traumatic stress disorder (PTSD)

Post-traumatic stress disorder (PTSD) is a neuropsychiatric disorder that occurs in approximately 15% of people as a result of some traumatic events. The main symptoms are re-experiencing and avoidance of everything related to this event and hyperarousal. The main component of the pathophysiology of PTSD is an imbalance in the functioning of the hypothalamic-pituitary-adrenal axis (HPA) and development of neuroinflammation. In parallel with this, mitochondrial dysfunction is observed, as in many other diseases. In this review, we focus on the question how mitochondria may be involved in the development of neuroinflammation and its maintaining at PTSD. First, we describe the differences in the operation of the neuro-endocrine system during stress versus PTSD. We then show changes in the activity/expression of mitochondrial proteins in PTSD and how they can affect the levels of hormones involved in PTSD development, as well as how mitochondrial damage/pathogen-associated molecule patterns (DAMPs/PAMPs) trigger development of inflammation. In addition, we examine the possibility of treating PTSD-related inflammation using mitochondria as a target.

Alterations of mitochondrial dynamics in serotonin transporter knockout rats: A possible role in the fear extinction recall mechanisms

Stress-related mental disorders encompass a plethora of pathologies that share the exposure to a negative environment as trigger for their development. The vulnerability to the effects of a negative environment is not equal to all but differs between individuals based on the genetic background makeup. Here, to study the molecular mechanisms potentially underlying increased threat anticipation, we employed an animal model showing this symptom (5-HTT knockout rats) which we exposed to Pavlovian fear conditioning (FC). We investigated the role of mitochondria, taking advantage of the recent evidence showing that the dynamic of these organelles is dysregulated after stress exposure. Behavioral experiments revealed that, during the second day of extinction of the FC paradigm, 5-HTT knockout (5-HTT-/-) animals showed a lack of fear extinction recall. From a mechanistic standpoint, we carried out our molecular analyses on the amygdala and prefrontal cortex, given their role in the management of the fear response due to their tight connection. We demonstrated that mitochondrial dynamics are impaired in the amygdala and prefrontal cortex of 5-HTT-/- rats. The dissection of the potential contributing factors revealed a critical role in the mechanisms regulating fission and fusion that are dysregulated in transgenic animals. Furthermore, mitochondrial oxidative phosphorylation, mitochondrial biogenesis, and the production of antioxidant enzymes were altered in these brain regions in 5-HTT-/- rats. In summary, our data suggest that increased extracellular 5-HT levels cause an unbalance of mitochondrial functionality that could contribute to the reduced extinction recall of 5-HTT-/- rats, pointing out the role of mitochondrial dynamics in the etiology of psychiatric disorders. Our findings, also, provide some interesting insights into the targeted development of drugs to treat such disorders.

Litopenaeus vannamei Sma and Mad related protein 5 gene is involved in stress response and white spot syndrome virus infection

Cell survival is based on the stability of intracellular state. It was well known that biochemical reactions in cells require specific intracellular environments, such as pH and calcium concentration. While the mechanism of stabilizing the intracellular environment is complex and far from clear. In this study, a Sma and Mad related protein 5 gene (LvSmad5) of Litopenaeus vannamei was cloned. LvSmad5 was located to both cytoplasm and nucleus. And subcellular localization of LvSmad5 was responsed to the changing of cells internal and external environment. Besides, it was found that subcellular localization of LvSmad5 was also regulated by unfolded protein response. Moreover, it was proved that nucleic localization of LvSmad5 could significantly increase the white spot syndrome virus (WSSV) infection in shrimp, and knockdown expression of LvSmad5 decreased the cumulative mortality of WSSV infection shrimp. Further investigation revealed that cytoplasm LvSmad5 could interplay with shrimp hexokinase 1, and contribute to glycolysis. These results indicated that LvSmad5 played a role in L. vannamei environmental stress response, and was used by WSSV for its replication.

Cerebellar and multi-system metabolic reprogramming associated with trauma exposure and post-traumatic stress disorder (PTSD)-like behavior in mice

Mitochondrial metabolism is increasingly implicated in psychopathologies and mood disorders, including post-traumatic stress disorder (PTSD). We recently reported that mice exposed to a novel paradigm for the induction of PTSD-like behavior displayed reduced mitochondrial electron transport chain (mtETC) complex activity as well as decreased multi-system fatty acid oxidation (FAO) flux. Based on these results, we hypothesized that stressed and PTSD-like animals would display evidence of metabolic reprogramming in both cerebellum and plasma consistent with increased energetic demand, mitochondrial metabolic reprogramming, and increased oxidative stress. We performed targeted metabolomics in both cerebellar tissue and plasma, as well as untargeted nuclear magnetic resonance (NMR) spectroscopy in the cerebellum of 6 PTSD-like and 7 resilient male mice as well as 7 trauma-naïve controls. We identified numerous differences in amino acids and tricarboxylic acid (TCA) cycle metabolite concentrations in the cerebellum and plasma consistent with altered mitochondrial energy metabolism in trauma exposed and PTSD-like animals. Pathway analysis identified metabolic pathways with significant metabolic pathway shifts associated with trauma exposure, including the tricarboxylic acid cycle, pyruvate, and branched-chain amino acid metabolism in both cerebellar tissue and plasma. Altered glutamine and glutamate metabolism, and arginine biosynthesis was evident uniquely in cerebellar tissue, while ketone body levels were modified in plasma. Importantly, we also identified several cerebellar metabolites (e.g. choline, adenosine diphosphate, beta-alanine, taurine, and myo-inositol) that were sufficient to discriminate PTSD-like from resilient animals. This multilevel analysis provides a comprehensive understanding of local and systemic metabolite fingerprints associated with PTSD-like behavior, and subsequently altered brain bioenergetics. Notably, several transformed metabolic pathways observed in the cerebellum were also reflected in plasma, connecting central and peripheral biosignatures of PTSD-like behavior. These preliminary findings could direct further mechanistic studies and offer insights into potential metabolic interventions, either pharmacological or dietary, to improve PTSD resilience.

Evaluation of the Effect of Prazosin Treatment on α-2c Adrenoceptor and Apoptosis Protein Levels in the Predator Scent-Induced Rat Model of Post-Traumatic Stress Disorder

The predator scent-induced (PSI) stress model is a rat model used to mimic post-traumatic stress disorder (PTSD) symptoms in humans. There is growing evidence that prazosin, which blocks α-1 and is approved by the FDA as an anti-hypertensive drug, can potentially be of use in the treatment of PTSD-related sleep disorders. The aim of this study was to investigate the role of prazosin treatment on behavioral parameters (freezing time, total transitions, and rearing frequency measured from the open field; anxiety index, total entries and time spent in open arms calculated from the elevated plus maze), apoptotic proteins and α-2c-AR in fear memory reconsolidation in the PSI stress rat model. We used western blot analysis to determine the effect of prazosin (0.5 mg/kg/ip) on α-2c-AR and apoptotic protein expression changes in the frontal cortex, hippocampus, and amygdala. It was determined that in the stress group, there was increased freezing time and anxiety index, and decreased rearing frequency, total transitions, total entries, and time spent in open arms compared to the control groups. Following PSI-stress, pro-apoptotic (bax) protein expression levels increased and α-2c AR and anti-apoptotic protein (bcl-2) levels decreased in investigated all brain regions. The majority of stress-induced changes were recovered with prazosin treatment. The results of our study may potentially be useful in understanding the effect of prazosin treatment, given the fact that the amygdala, frontal cortex, and hippocampus regions are affected for stress conditions.

Metabolism, Metabolomics, and Inflammation in Posttraumatic Stress Disorder

Posttraumatic stress disorder (PTSD) is defined by classic psychological manifestations, although among the characteristics are significantly increased rates of serious somatic comorbidities, such as cardiovascular disease, immune dysfunction, and metabolic syndrome. In this review, we assess the evidence for disturbances that may contribute to somatic pathology in inflammation, metabolic syndrome, and circulating metabolites (implicating mitochondrial dysfunction) in individuals with PTSD and in animal models simulating features of PTSD. The clinical and preclinical data highlight probable interrelated features of PTSD pathophysiology, including a proinflammatory milieu, metabolomic changes (implicating mitochondrial and other processes), and metabolic dysregulation. These data suggest that PTSD may be a systemic illness, or that it at least has systemic manifestations, and the behavioral manifestations are those most easily discerned. Whether somatic pathology precedes the development of PTSD (and thus may be a risk factor) or follows the development of PTSD (as a result of either shared pathophysiologies or lifestyle adaptations), comorbid PTSD and somatic illness is a potent combination placing affected individuals at increased physical as well as mental health risk. We conclude with directions for future research and novel treatment approaches based on these abnormalities.

PERK signalling pathway mediates single prolonged stress-induced dysfunction of medial prefrontal cortex neurons

Post-traumatic stress disorder (PTSD) is characterized with abnormal learning and memory. Impairments in learning and memory are closely associated with apoptosis in the medial prefrontal cortex (mPFC). We previously examined the endoplasmic reticulum (ER) stress was involved in the apoptosis in the mPFC of PTSD. The PERK pathway plays the important role in the ER stress-induced apoptosis. The aim of the present study was to explore the role of PERK pathway in neuronal apoptosis in the mPFC of rat models of PTSD. We used the single prolonged stress (SPS) to mimic PTSD in rats and studied the effects of the PERK pathway in mPFC. Learning and memory behavior were examined by Morris water maze and novel object recognition tests. Apoptosis in mPFC was detected by TUNEL staining. Our results showed decreased learning memory and increased apoptosis of mPFC neurons in rats exposed to SPS. SPS exposure upregulate mRNA expressions of PERK, p-PERK, eIF2α, p-eIF2α, nuclear ATF4 and C/EBP-homologous protein (CHOP) in mPFC neurons, but the protein levels of these molecules showed difference in magnitude and time course. GSK2606414 (an antagonist of PERK) treatment successfully reversed the above changes. These results suggested that the PERK pathway mediated SPS-induced neural apoptosis in the mPFC. These findings will be helpful in understanding mPFC-related pathogenesis of PTSD.

Impaired PARP activity in response to the β-adrenergic receptor agonist isoproterenol

Psychological stress has been associated with DNA damage, thus increasing the risk of numerous diseases including cancer. Here, we investigate the effect of acute and chronic stress on poly(ADP-ribose) polymerase-1 (PARP-1), a sensor of DNA damage and DNA repair initiator. In order to mimic the chronic release of epinephrine, human peripheral blood mononuclear cells (PBMCs) were treated repeatedly with the sympathomimetic drug isoproterenol. We found significant induction of DNA strand breaks that remained unrepaired 24 h after ex vivo incubation. Isoproterenol-induced DNA strand breaks could be partially prevented by pre-treatment with the β-adrenergic receptor antagonist propranolol. Furthermore, the level of PARP-1 protein and PARP activity decreased and the levels of the PARP substrate nicotinamide adenine dinucleotide (NAD⁺) and of adenosine triphosphate (ATP), necessary to replenish NAD⁺ pools, were lowered by isoproterenol treatment. In conclusion our data provide novel insights into the mechanisms of isoproterenol-induced genotoxicity linking β-adrenergic stimulation and PARP-1.

Single-Prolonged Stress: A Review of Two Decades of Progress in a Rodent Model of Post-traumatic Stress Disorder

Post-traumatic stress disorder (PTSD) is a common, costly, and often debilitating psychiatric condition. However, the biological mechanisms underlying this disease are still largely unknown or poorly understood. Considerable evidence indicates that PTSD results from dysfunction in highly-conserved brain systems involved in stress, anxiety, fear, and reward. Pre-clinical models of traumatic stress exposure are critical in defining the neurobiological mechanisms of PTSD, which will ultimately aid in the development of new treatments for PTSD. Single prolonged stress (SPS) is a pre-clinical model that displays behavioral, molecular, and physiological alterations that recapitulate many of the same alterations observed in PTSD, illustrating its validity and giving it utility as a model for investigating post-traumatic adaptations and pre-trauma risk and protective factors. In this manuscript, we review the present state of research using the SPS model, with the goals of (1) describing the utility of the SPS model as a tool for investigating post-trauma adaptations, (2) relating findings using the SPS model to findings in patients with PTSD, and (3) indicating research gaps and strategies to address them in order to improve our understanding of the pathophysiology of PTSD.

Using c-Jun to identify fear extinction learning-specific patterns of neural activity that are affected by single prolonged stress

Neural circuits via which stress leads to disruptions in fear extinction is often explored in animal stress models. Using the single prolonged stress (SPS) model of post traumatic stress disorder and the immediate early gene (IEG) c-Fos as a measure of neural activity, we previously identified patterns of neural activity through which SPS disrupts extinction retention. However, none of these stress effects were specific to fear or extinction learning and memory. C-Jun is another IEG that is sometimes regulated in a different manner to c-Fos and could be used to identify emotional learning/memory specific patterns of neural activity that are sensitive to SPS. Animals were either fear conditioned (CS-fear) or presented with CSs only (CS-only) then subjected to extinction training and testing. C-Jun was then assayed within neural substrates critical for extinction memory. Inhibited c-Jun levels in the hippocampus (Hipp) and enhanced functional connectivity between the ventromedial prefrontal cortex (vmPFC) and basolateral amygdala (BLA) during extinction training was disrupted by SPS in the CS-fear group only. As a result, these effects were specific to emotional learning/memory. SPS also disrupted inhibited Hipp c-Jun levels, enhanced BLA c-Jun levels, and altered functional connectivity among the vmPFC, BLA, and Hipp during extinction testing in SPS rats in the CS-fear and CS-only groups. As a result, these effects were not specific to emotional learning/memory. Our findings suggest that SPS disrupts neural activity specific to extinction memory, but may also disrupt the retention of fear extinction by mechanisms that do not involve emotional learning/memory.

Brain atrophy in the visual cortex and thalamus induced by severe stress in animal model

Psychological stress induces many diseases including post-traumatic stress disorder (PTSD); however, the causal relationship between stress and brain atrophy has not been clarified. Applying single-prolonged stress (SPS) to explore the global effect of severe stress, we performed brain magnetic resonance imaging (MRI) acquisition and Voxel-based morphometry (VBM). Significant atrophy was detected in the bilateral thalamus and right visual cortex. Fluorescent immunohistochemistry for Iba-1 as the marker of activated microglia indicates regional microglial activation as stress-reaction in these atrophic areas. These data certify the impact of severe psychological stress on the atrophy of the visual cortex and the thalamus. Unexpectedly, these results are similar to chronic neuropathic pain rather than PTSD clinical research. We believe that some sensitisation mechanism from severe stress-induced atrophy in the visual cortex and thalamus, and the functional defect of the visual system may be a potential therapeutic target for stress-related diseases.

Using the Single Prolonged Stress Model to Examine the Pathophysiology of PTSD

The endurance of memories of emotionally arousing events serves the adaptive role of minimizing future exposure to danger and reinforcing rewarding behaviors. However, following a traumatic event, a subset of individuals suffers from persistent pathological symptoms such as those seen in posttraumatic stress disorder (PTSD). Despite the availability of pharmacological treatments and evidence-based cognitive behavioral therapy, a considerable number of PTSD patients do not respond to the treatment, or show partial remission and relapse of the symptoms. In controlled laboratory studies, PTSD patients show deficient ability to extinguish conditioned fear. Failure to extinguish learned fear could be responsible for the persistence of PTSD symptoms such as elevated anxiety, arousal, and avoidance. It may also explain the high non-response and dropout rates seen during treatment. Animal models are useful for understanding the pathophysiology of the disorder and the development of new treatments. This review examines studies in a rodent model of PTSD with the goal of identifying behavioral and physiological factors that predispose individuals to PTSD symptoms. Single prolonged stress (SPS) is a frequently used rat model of PTSD that involves exposure to several successive stressors. SPS rats show PTSD-like symptoms, including impaired extinction of conditioned fear. Since its development by the Liberzon lab in 1997, the SPS model has been referred to by more than 200 published papers. Here we consider the findings of these studies and unresolved questions that may be investigated using the model.

Antidepressant-like activity of venlafaxine and clonidine in mice exposed to single prolonged stress - A model of post-traumatic stress disorder. Pharmacodynamic and molecular docking studies

BACKGROUND

Post-traumatic stress disorder (PTSD) is a growing issue worldwide characterized by stress and anxiety in response to re-experiencing traumatic events which strongly impair patient's quality of life and social functions. Available antidepressant and anxiolytic drugs are not efficacious in the majority of treated individuals. This necessitates a significant medical demand to develop novel therapeutic strategies for PTSD.

EXPERIMENTAL APPROACH

Animal model of PTSD was induced using a mouse single prolonged stress protocol (mSPS). To assess the activity of venlafaxine and clonidine, the forced swim test (FST) was used repeatedly 24h, 3days, 8days, 15days and 25days after mSPS. To get insight into a possible mechanism of anti-PTSD action, molecular docking procedure was utilized for the most active drug. This in silico part comprised molecular docking of enantiomers of venlafaxine to human transporters for serotonin (hSERT), norepinephrine (hNET) and dopamine (hDAT).

KEY RESULTS

In mSPS-subjected mice FST revealed the effectiveness of venlafaxine, however in non SPS-subjected mice both venlafaxine and clonidine were active. Molecular docking studies indicated that the affinity of venlafaxine to monoamine transporters is growing in the following rank order: hDAT<hNET<hSERT. Both venlafaxine enantiomers present different selectivity and binding mode.

CONCLUSION AND IMPLICATIONS

Venlafaxine but not clonidine was effective in an animal model of PTSD. Its mechanism of action, i.e., SERT, NET and DAT inhibition indicates potential drug targets for PTSD treatment. We expect that these results will contribute to a broader application of VLX in PTSD patients.

Effects of a simulated wolf encounter on brain and blood biomarkers of stress-related psychological disorders in beef cows with or without previous exposure to wolves

This experiment compared mRNA expression of brain-blood biomarkers associated with stress-related psychological disorders, including post-traumatic stress disorder (PTSD), in beef cows from wolf-naïve and wolf-experienced origins that were subjected to a simulated wolf encounter. Multiparous, non-pregnant, non-lactating Angus-crossbred cows from the Eastern Oregon Agricultural Research Center (Burns, OR; CON; = 10) and from a commercial operation near Council, ID (WLF; = 10) were used. To date, gray wolves are not present around Burns, OR, and thus CON were naïve to wolves. Conversely, wolves are present around Council, ID, and WLF cows were selected from a herd that had experienced multiple wolf-predation episodes from 2008 to 2015. After a 60-d commingling and adaptation period, CON and WLF cows were allocated to groups A or B (d -1; 5 CON and 5 WLF cows in each group). On d 0, cows from group A were sampled for blood and immediately slaughtered, and samples were analyzed to evaluate inherent differences between CON and WLF cows. On d 1, cows from group B were exposed in pairs (1 CON and 1 WLF cow) to experimental procedures. Cows were sampled for blood, moved to 2 adjacent drylot pens (1 WLF and 1 CON cow/pen) and subjected to a simulated wolf encounter event for 20 min. The encounter consisted of (1) cotton plugs saturated with wolf urine attached to the drylot fence, (2) reproduction of wolf howls, and (3) three leashed dogs that were walked along the fence perimeter. Thereafter, another blood sample was collected and cows were slaughtered. Upon slaughter, the brain was removed and dissected for collection of the hypothalamus, and one longitudinal slice of the medial pre-frontal cortex, amygdala, and Cornu Ammonis (1 region of the hippocampus from both hemispheres). Within cows from group A, expression of in hippocampus and amygdala were greater ( < 0.01) in WLF vs. CON cows. Within cows from group B, expression of hippocampal mRNA and expression of c mRNA in hippocampus and amygdala were less ( ≤ 0.04) in WLF vs. CON cows. These are key biological markers known to be downregulated during stress-related psychological disorders elicited by fear, particularly PTSD. Hence, cows originated from a wolf-experienced herd presented biological evidence suggesting a psychological disorder, such as PTSD, after the simulated wolf encounter when compared with cows originated from a wolf-naïve herd.

Neural circuits via which single prolonged stress exposure leads to fear extinction retention deficits

Single prolonged stress (SPS) has been used to examine mechanisms via which stress exposure leads to post-traumatic stress disorder symptoms. SPS induces fear extinction retention deficits, but neural circuits critical for mediating these deficits are unknown. To address this gap, we examined the effect of SPS on neural activity in brain regions critical for extinction retention (i.e., fear extinction circuit). These were the ventral hippocampus (vHipp), dorsal hippocampus (dHipp), basolateral amygdala (BLA), prelimbic cortex (PL), and infralimbic cortex (IL). SPS or control rats were fear conditioned then subjected to extinction training and testing. Subsets of rats were euthanized after extinction training, extinction testing, or immediate removal from the housing colony (baseline condition) to assay c-Fos levels (measure of neural activity) in respective brain region. SPS induced extinction retention deficits. During extinction training SPS disrupted enhanced IL neural activity and inhibited BLA neural activity. SPS also disrupted inhibited BLA and vHipp neural activity during extinction testing. Statistical analyses suggested that SPS disrupted functional connectivity within the dHipp during extinction training and increased functional connectivity between the BLA and vHipp during extinction testing. Our findings suggest that SPS induces extinction retention deficits by disrupting both excitatory and inhibitory changes in neural activity within the fear extinction circuit and inducing changes in functional connectivity within the Hipp and BLA.

Changes in integrin αv, vinculin and connexin43 in the medial prefrontal cortex in rats under single-prolonged stress

Post‑traumatic stress disorder (PTSD) is a stress‑accociated mental disorder that occurs as a result of exposure to a traumatic event, with characteristic symptoms, including intrusive memories, hyperarousal and avoidance. The medial prefrontal cortex (mPFC) is known to be significantly involved in emotional adjustment, particularly introspection, inhibition of the amygdala and emotional memory. Previous structural neuroimaging studies have revealed that the mPFC of PTSD patients was significantly smaller when compared with that of controls and their emotional adjustment function was weakened. However, the mechanisms that cause such atrophy remain to be elucidated. The aim of the present study was to elucidate the possible mechanisms involved in apoptosis induced by single‑prolonged stress (SPS) in the mPFC of PTSD rats. SPS is an animal model reflective of PTSD. Of the proposed animal models of PTSD, SPS is one that has been shown to be reliably reproducible in patients with PTSD. Wistar rats were sacrificed at 1, 4, 7 and 14 days after exposure to SPS. Apoptotic cells were assessed using electron microscopy and the TUNEL method. Expression of integrin αv, vinculin and connexin43 were detected using immunohistochemistry, western blotting and reverse transcription polymerase chain reaction. The present results demonstrated that apoptotic cells significantly increased in the mPFC of SPS rats, accompanied with changes in expression of integrin αv, vinculin and connexin43. The present results indicated that SPS‑induced apoptosis in the mPFC of PTSD rats and the mitochondrial pathway were involved in the process of SPS‑induced apoptosis.

Effect of glucose-regulated protein 94 and endoplasmic reticulum modulator caspase-12 in medial prefrontal cortex in a rat model of posttraumatic stress disorder

Posttraumatic stress disorder (PTSD) is an anxiety disorder caused by a life-threatening traumatic experience, which affects a patient's quality of life and social stability. The objective of this study was to investigate the change of the glucose-regulated protein (GRP) 94 and apoptosis-related caspase-12 expression in medial prefrontal cortex (mPFC) in rats to determine whether endoplasmic reticulum apoptosis pathway plays an important role in single-prolonged stress (SPS), a well-established PTSD animal model, and therefore to provide experimental evidence to reveal PTSD pathogenesis. A total of 120 healthy male Wistar rats were selected for this study, randomly divided into a normal control group and SPS groups of 1, 4, 7, 14, and 28 days. Behavioral studies of the learning and memory capabilities of rats were observed by using Morris water maze. Morphological changes were detected using transmission electron microscopy (TEM). Immunohistochemistry, Western blot, and reverse transcription polymerase chain reaction (RT-PCR) were used to detect the expressions of caspase-12 and GRP94 expressions in mPFC. Our results showed that compared with control groups, after the SPS exposure, the average escape latency was prolonged in place navigation test (P < 0.05), and swimming time in the third quadrant in spatial probe test shortened. The morphological change of mPFC in each SPS group bears typical apoptotic characteristics. The expressions of GRP94 and caspase-12 gradually increased on 1 and 4 days, peaked on 7 days after the SPS exposure, and then decreased. These results suggest that SPS exposure can induce apoptotic neurons and a change of caspase-12 and GRP94 expression in the mPFC, which may be one of the pathogenesis of mPFC abnormal function in PTSD.

Changes in the expression of the vitamin D receptor and LVSCC‑A1C in the rat hippocampus submitted to single prolonged stress

Vitamin D signaling not only controls calcium (Ca2+) and phosphorus uptake and transport, but also correlates with neurocognitive decline and neurodegenerative diseases. Almost all actions of Vitamin D are mediated by the transcription factor, vitamin D receptor (VDR), which has been widely identified in the central nervous system. Although previous studies have substantially advanced the understanding of the action of VDR in the brain, much remains unknown concerning how VDR relates to stress. Multiple lines of evidence indicate that the downregulation of L-type voltage-sensitive Ca2+-channels α-1C (LVSCC-A1C) by vitamin D in hippocampal neurons is able to reduce the influx and excitotoxic effects of Ca2+ to neurons. Along these lines, the purpose of the present study was to analyze the relative expression of VDR in the hippocampus of rats exposed to single prolonged stress (SPS) as a putative animal model for human post-traumatic stress disorder (PTSD). Furthermore, changes in the levels of expression of LVSCC-A1C and Ca2+ (neurotransmitter content) were examined during the onset periods of PTSD. The results revealed an increase in the expression of VDR at 1, 3 and 7 days post-stress compared with the control group. The intracellular free Ca2+ levels in the hippocampus increased 1 day after SPS exposure, and then decreased gradually to the normal level at 14 days, consistent with the expression pattern of LVSCC-A1C. These results indicated that VDR may be involved in the pathogenesis of SPS rats, thereby providing an alternative preparation to search for optimal therapeutic strategies for PTSD.

Increased neuronal apoptosis in medial prefrontal cortex is accompanied with changes of Bcl-2 and Bax in a rat model of post-traumatic stress disorder

Post-traumatic stress disorder (PTSD) is an anxiety disorder caused by traumatic experience, which affects a patient's quality of life and social stability. The objective of this study was to determine the apoptosis-related genes B-cell lymphoma 2 (Bcl-2) and BCL2-associated X (Bax) expressions and medial prefrontal cortex (mPFC) neuronal apoptosis after PTSD in rat model and therefore to provide experimental evidence to reveal PTSD pathogenesis. The single-prolonged stress (SPS) method was used to set up the rat PTSD models. Chemiluminescence was used to determine serum corticosterone levels. Neuronal apoptosis was detected using transmission electron microscopy, Hoechst staining, and terminal deoxynucleotidyl transferase dUTP nick end labeling staining. Immunohistochemistry, immunofluorescence, RT-PCR, and Western blot were used to detect the expressions of Bcl-2 and Bax protein in mPFC. Our results showed an increased mPFC neuronal apoptosis after SPS stimulation. The number of apoptotic cells peaked on day 7. The expressions of Bcl-2 and Bax peaked on days 4 and 7. The Bcl-2/Bax ratio elevated on days 1 and 4 but decreased markedly on day 7. These results indicated that SPS stimulation increased the number of apoptotic neurons, up-regulated the expressions of Bcl-2 and Bax, and altered the Bcl-2/Bax ratio in the mPFC of PTSD rats.

A review on animal models for screening potential anti-stress agents

Stress is a state of threatened homeostasis that produces different physiological as well as pathological changes depending on severity, type and duration of stress. The animal models are pivotal for understanding the pathophysiology of stress-induced behavioral alterations and development of effective therapy for its optimal management. A battery of models has been developed to simulate the clinical pain conditions with diverse etiology. An ideal animal model should be able to reproduce each of the aspects of stress response and should be able to mimic the natural progression of the disease. The present review describes the different types of acute and chronic stress models including immersion in cold water with no escape, cold environment isolation, immobilization/restraint-induced stress, cold-water restraint stress, electric foot shock-induced stress, forced swimming-induced stress, food-deprived activity stress, neonatal isolation-induced stress, predatory stress, day-night light change-induced stress, noise-induced stress, model of post-traumatic stress disorder and chronic unpredictable stress models.