Animal Model Of Post-traumatic Stress Disorder Research Articles

Re‐exposure to a Traumatic Event Amplifies the Duration and Severity of Co‐morbid Chronic Pain in an Animal Model of Post‐traumatic Stress Disorder

Post‐traumatic stress disorder (PTSD) is a debilitating condition affecting up to 35% of combat veterans and between 7–8% of the general populace. Heightened anxiety/hyperarousal and chronic pain commonly co‐occur in both civilian and veteran PTSD populations. The shared co‐morbidity of PTSD with chronic pain negatively impacts the treatment of both disorders. Single‐prolonged stress (SPS) is an established animal model of PTSD capable of facilitating development of symptoms similar to those observed in human patients, including decreased pain threshold and amplified anxiety and fear responses. We have reported that SPS produces tactile allodynia that persists for over 5 weeks following the initial stress exposure. Many PTSD patients have experienced multiple traumatic events, and/or re‐experience the stress following exposure to reminders (cues) of that traumatic event. Because the severity of PTSD in humans correlates with the severity of the trauma, we felt it important to explore how re‐exposure to one of the original stressors altered the severity of existing co‐morbid nociceptive hypersensitivity. Therefore we have introduced a latent re‐stress component to the established SPS model in order to better understand how re‐exposure to a traumatic event may alter the duration and intensity of PTSD and co‐morbid symptoms and their molecular underpinnings.Male Sprague‐Dawley rats were subjected to single prolonged stress (SPS) at day 0. At day 21, half of the SPS rats were re‐stressed with 2 hour restraint, one of the original SPS stressors. The development of PTSD and co‐morbid symptoms was monitored over the course of 60 days by weekly nociception assessment using the von Frey assay for mechanical nociceptive sensitivity and Hargreaves’ assay for thermal nociceptive sensitivity. Anxiety was assessed by elevated plus maze at days 9, 30, and 51 of the initial SPS and days 9 and 21 of the re‐stressed group. Results from nociceptive testing indicate a prolonged and significant decrease in pain threshold of rats subjected to SPS + re‐stress as compared to SPS alone. Preliminary studies indicate that anxiety symptoms persisted for up to 52 days.Our results indicate that exposure to a re‐stress event following SPS increased the severity and duration of nociceptive hypersensitivity and anxiety in an animal model of PTSD. These findings suggest that the molecular markers that changed with SPS alone also will be found to exhibit exacerbated intensity and/or duration of effect following re‐stress. Future studies will examine those molecular changes following re‐stress with the goal of improving treatment and preventing continued deterioration following PTSD.These studies were approved by the OUHSC IACUC committee and conformed to the FASEB Statement of Principles for the use of animals in research and education.Support or Funding InformationUniversity of Oklahoma Health Sciences Center Vice President for Research and the Presbyterian Health Foundation Bridge Grant Program

Impaired Autonomic Regulation in Posttraumatic Stress Disorder

Post‐traumatic stress disorder (PTSD) is associated with a significantly increased risk of cardiovascular disease (CVD) and accumulating clinical evidence suggests that autonomic dysregulation due to sympathetic overactivity and/or parasympathetic insufficiency may contribute to progression of CVD in PTSD. Therefore, utilizing a translational approach, we sought to examine autonomic function in both a clinical PTSD population as well as in an animal model of PTSD. In experimental studies, mice were instrumented with radiotelemetry probes to evaluate autonomic indices following Pavlovian fear conditioning. Fear conditioning involves the pairing of a conditioned stimulus (e.g. tone) paired with an aversive uconditioned stimulus (e.g. foot shock) that evokes a conditioned response (e.g. freezing). Twenty‐four hours following fear conditioning, spectral analysis of heart rate was performed and the low‐to high‐frequency ratio (LF:HF) was used as an index of sympathovagal balance. Fear conditioned animals displayed a significant increase in the LF:HF ratio relative to baseline (1.21 ± 0.46; p<0.05) indicating a shift in sympathovagal balance. Two weeks following fear conditioning, we assessed the contribution of sympathetic activity to the maintenance of blood pressure using the ganglionic blocker chlorisondamine (12ug/g i.p.). In response to sympathetic nervous system blockade, fear conditioned animals had a greater fall in blood pressure compared to control (Δ Systolic −71.7± 1.9 vs −39.8 ± 5.8 mmHg; p<0.05). Collectively, these results suggest impairments in autonomic control in an animal model of PTSD prior to the onset of CVD. Finally, these findings will be compared to an ongoing clinical study using a population of combat‐related PTSD (n=13) versus age‐matched controls without PTSD (n=9). Continuous elecrocardiography, beat‐to‐beat arterial blood pressure (BP) measurements, and 24‐hour ambulatory BP measurements have been collected at rest, during, and following mental stress. In an effort to translate our pre‐clinical results, these data will be analyzed for spectral analysis of heart rate variability, BP variability, and 24‐hour ambulatory BP patterns.Support or Funding InformationNIH R00 HL107675‐03 American Heart Association ‐ 15CSA24340001

Exacerbated Headache‐Related Pain in the Single Prolonged Stress Model of Post‐traumatic Stress Disorder

Post‐traumatic stress disorder (PTSD) frequently shares co‐morbidity with chronic pain and negatively impacts the course of treatment for both disorders. Single‐prolonged stress (SPS), an established animal model for PTSD, models many of the symptoms of PTSD reported in humans including exaggerated negative feedback of the HPA axis, hypocortisolism, enhanced fear and anxiety responses and cognitive impairment. We and others reported that SPS induces long‐lasting mechanical and thermal allodynia and visceral and inflammatory hypersensitivity. Chronic headache pain is one of the most commonly reported co‐morbid pain conditions by PTSD patients and one of the most resistant to effective treatment, yet this has never been modeled in an animal model of PTSD. We modified the chronic headache pain model recently developed by Pradhan and colleagues (2014) to investigate the contribution of SPS to sodium nitroprusside (SNP)‐induced hyperalgesia. SPS and control Sprague Dawley rats were randomly divided into SNP or vehicle‐treated groups. SNP (2 mg/kg, i.p.) was injected every second day from day 7 to 15 after initiation of SPS. Rat paw withdrawal threshold (PWT) to von Frey stimuli and tail flick latencies (TFL) dramatically decreased as early as 7 days after SPS and lasted until at least day 21. Basal PWT and TFL, as assessed prior to each SNP administration, also significantly decreased during the SNP treatment period. The lower pain thresholds recovered 7 days following the final SNP injection in SNP group, but not in SPS/SNP group. Nociceptin/orphanin FQ (N/OFQ) plays an important role in maintenance of hyperalgesia and allodynia following SPS. Elevated N/OFQ levels observed in cerebrospinal fluid (CSF) of SPS rats were even higher in CSF of the SPS/SNP group. Real‐time PCR revealed that glial fibrillary acidic protein (GFAP) and N/OFQ peptide (NOP) receptor mRNA expression increased in dorsal root ganglia (DRG) 21 days after SPS exposure; mRNA increases in the SPS/SNP group was more pronounced than SPS or SNP alone. PreproN/OFQ mRNA expression decreased in both SPS and SPS/SNP rats compared to control, but no difference was observed between the two groups. SNP treatment alone did not alter GFAP, NOP receptor or N/OFQ mRNA levels in DRG. Significant interaction between SNP and SPS was noted following immunoblot analysis of TNF alpha protein expression in DRG and NOP receptor expression in trigeminal ganglia. Our results indicate that chronic SNP‐induced nociceptive hypersensitivity (headache pain) is exaggerated in rats exposed to PTSD, and that N/OFQ may play an important role in the interaction between SPS and SNP.The animal protocol was approved by the OUHSC IACUC committee; studies conformed to the FASEB Statement of Principles for the use of animals in research and education.Support or Funding InformationUniversity of Oklahoma Health Sciences Center Vice President for Research and Presbyterian Health Foundation Bridge Grant Programs.

Effects of In utero environment and maternal behavior on neuroendocrine and behavioral alterations in a mouse model of prenatal trauma.

Maternal posttraumatic stress disorder (PTSD) following trauma exposure during pregnancy is associated with an increased risk of affective disorders in children. To investigate the mechanisms by which prenatal trauma and/or maternal PTSD affect brain development and behavior we established a mouse model of prenatal traumatic (PT) experience based on the application of an electric foot shock to C57Bl/6N female mice on the gestational day 12 during their pregnancy. The model is based on a previously validated animal model of PTSD. We found high anxiety levels and poor maternal care along with reduced serum prolactin and increased corticosterone levels in dams following maternal trauma (MT). PT-pups were born smaller and stayed smaller throughout their life. We show increased time and frequency of ultrasonic calls in PT-pups when separated from the mothers on the postnatal day (PND) 9. Cross-fostering experiments reveal lower anxiety levels in PT pups raised by healthy mothers as compared to trauma-naive pups raised by MT-dams. Importantly, the combination of prenatal trauma and being raised by a traumatized mother leads to: (1) the highest corticosterone levels in pups, (2) longest USV-call time and (3) highest anxiety levels in comparison to other experimental groups. Our data indicates a distinct change in maternal care following MT which is possibly associated with trauma-induced decrease in prolactin levels. Furthermore, we show that maternal behavior is crucial for the development of the offspring anxiety and specific aspects in maternal care overwrite to a significant extend the effects of in utero and postnatal environment. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 76: 1254-1265, 2016.

Behavioral profiling as a translational approach in an animal model of posttraumatic stress disorder

Diagnosis of psychiatric disorders in humans is based on comparing individuals to the normal population. However, many animal models analyze averaged group effects, thus compromising their translational power. This discrepancy is particularly relevant in posttraumatic stress disorder (PTSD), where only a minority develop the disorder following a traumatic experience.In our PTSD rat model, we utilize a novel behavioral profiling approach that allows the classification of affected and unaffected individuals in a trauma-exposed population.Rats were exposed to underwater trauma (UWT) and four weeks later their individual performances in the open field and elevated plus maze were compared to those of the control group, allowing the identification of affected and resilient UWT-exposed rats.Behavioral profiling revealed that only a subset of the UWT-exposed rats developed long-lasting behavioral symptoms. The proportion of affected rats was further enhanced by pre-exposure to juvenile stress, a well-described risk factor of PTSD.For a biochemical proof of concept we analyzed the expression levels of the GABAA receptor subunits α1 and α2 in the ventral, dorsal hippocampus and basolateral amygdala. Increased expression, mainly of α1, was observed in ventral but not dorsal hippocampus of exposed animals, which would traditionally be interpreted as being associated with the exposure-resultant psychopathology. However, behavioral profiling revealed that this increased expression was confined to exposed-unaffected individuals, suggesting a resilience-associated expression regulation. The results provide evidence for the importance of employing behavioral profiling in animal models of PTSD, in order to better understand the neural basis of stress vulnerability and resilience.

Involvement of allopregnanolone in the anti-PTSD-like effects of AC-5216

Cholesterol import into mitochondria through the translocator protein (18 KDa) (TSPO) is the starting point and an important rate-limiting step in neurosteroidogenesis. For this reason TSPO has received increased attention in the pathophysiology of post-traumatic stress disorder (PTSD). In an effort to explore the role of TSPO in mediating the anti-PTSD effect, we first assessed the effects of the TSPO ligand AC-5216 in alleviating the enhanced anxiety and fear response in a time-dependent sensitization (TDS) procedure, a rat PTSD animal model. In the present study, we showed that chronic treatment with AC-5216 caused significant suppression of the enhanced anxiety and contextual fear induced in post-TDS rats; these effects were blocked by PK11195. Furthermore, AC-5216 treatment increased the levels of allopregnanolone in the serum, prefrontal cortex, and hippocampus of post-TDS rats, and these effects were antagonized by PK11195. These results demonstrate that AC-5216 has a clear anti-PTSD-like effect, which might be partially mediated by binding to TSPO and the subsequent synthesis of allopregnanolone.

Behavioral changes over time in post-traumatic stress disorder: Insights from a rat model of single prolonged stress

Post-traumatic stress disorder (PTSD) is manifested as a persistent mental and emotional condition after potentially life-threatening events. Different animal models of PTSD have been developed for neuro-pathophysiology and pharmacological evaluations. A single prolonged stress (SPS) induced animal model has demonstrated to result in specific neuro-endocrinological dysregulation, and behavior abnormalities observed in PTSD. However, animal studies of PTSD have mostly been performed at one time point after SPS exposure. To better understand the development of PTSD-like behaviors in the SPS animal model, and to identify an optimal period of study, we examined depressive behavior, anxiety-like behavior, physical activity and body weight in SPS model rats for two weeks. Our results confirmed the SPS-induced PTSD-like behavior and physical activity observed in previous studies, and indicated that the most pronounced symptomatic behavior changes were observed on day 1 and 7 after SPS exposure, which may involve stress-induced acute hormone changes and unclear secondary neurobiological changes, respectively. These results provide a solid basis for further investigation into the neuro-pathophysiology of or neuropharmacology for PTSD using the SPS rat model. However, for chronic (pharmacological) studies longer than 7 days, a prolonged PTSD animal model should be developed, perhaps using enhanced stimulation.

NOX2 Mediated-Parvalbumin Interneuron Loss Might Contribute to Anxiety-Like and Enhanced Fear Learning Behavior in a Rat Model of Post-Traumatic Stress Disorder.

Post-traumatic stress disorder (PTSD) is a common psychiatric disease following exposure to a severe traumatic event or physiological stress, yet the precise mechanisms underlying PTSD remains largely to be determined. Using an animal model of PTSD induced by a single prolonged stress (SPS), we assessed the role of hippocampal nicotinamide adenosine dinucleotide phosphate (NADPH) oxidase 2 (NOX2) and parvalbumin (PV) interneurons in the development of PTSD symptoms. In the present study, behavioral tests were performed by the open field (day 13 after SPS) and fear conditioning tests (days 13 and 14 after SPS). For the interventional study, rats were chronically treated with a NADPH oxidase inhibitor apocynin either by early or delayed administration. The levels of tumor necrosis factor-alpha, interleukin (IL)-1β, IL-6, IL-10, malondialdehyde, superoxide dismutase, NOX2, 4-hydroxynonenal, and PV in the hippocampus were measured at the indicated time points. In the present study, we showed that SPS rats displayed anxiety-like and enhanced fear learning behavior, which was accompanied by the increased expressions of malondialdehyde, IL-6, NOX2, 4-hydroxynonenal, and decreased PV expression. Notably, early but not delayed treatment with apocynin reversed all these abnormalities after SPS. In conclusion, our results provided evidence that NOX2 activation in the hippocampus, at least in part, contributes to oxidative stress and neuroinflammation, which further results in PV interneuron loss and consequent PTSD symptoms in a rat model of PTSD induced by SPS.

Single-prolonged stress induce different change in the cell organelle of the hippocampal cells: A study of ultrastructure

MRI studies have revealed structural and functional changes in the hippocampus of post-traumatic stress disorder (PTSD) patients. Previous studies conducted by us in a PTSD animal model found that single prolonged stress (SPS) induced abnormal morphological changes in hippocampal cells. The effects of SPS on cellular organelles of the hippocampal neurons remain unknown; however, these changes have been involved in SPS-induced abnormal hippocampal function. The aim of the present study is to examine ultrastructural changes in cellular organelles, including the lysosomes, mitochondria (Mit), Golgi apparatus, and endoplasmic reticulum (ER), following SPS exposure using transmission electron microscopy, enzyme histochemistry, and enzyme cytochemistry. First, morphological changes of the hippocampal cells and ultrastructural changes in cellular organelles, including lysosomes, ER, and Mit-induced by SPS were observed. Results from histo- and cytochemistry demonstrated that the Mit marker enzyme, cytochrome c oxidase (COX), and the lysosomal enzyme acid phosphatase, (ACP), increased following exposure to SPS. SPS induced COX release from Mit and led to a wider distribution of ACP in round lysosomes, NLY, and the Golgi. In addition, we found that SPS increased the presence of autophagosomes and induced changes in the autophagy-related protein, Beclin. These results indicated the differential effects of SPS on cellular organelles, that is, a positive effect on lysosomes as well as a negative effect on the Mit and ER. Increased lysosomal function may serve as protection against SPS-induced cell damage. Structural changes in the Mit and ER may be involved in SPS-induced disorders of energy metabolism and protein synthesis and export.

Candesartan ameliorates impaired fear extinction induced by innate immune activation

Patients with post-traumatic stress disorder (PTSD) tend to show signs of a relatively increased inflammatory state suggesting that activation of the immune system may contribute to the development of PTSD. In the present study, we tested whether activation of the innate immune system can disrupt acquisition or recall of auditory fear extinction using an animal model of PTSD. Male adolescent rats received auditory fear conditioning in context A. The next day, an intraperitoneal injection of lipopolysaccharide (LPS; 100μg/kg) prior to auditory fear extinction in context B impaired acquisition and recall of extinction. LPS (100μg/kg) given after extinction training did not impair extinction recall suggesting that LPS did not affect consolidation of extinction. In contrast to cued fear extinction, contextual fear extinction was not affected by prior injection of LPS (100μg/kg). Although LPS also reduced locomotion, we could dissociate the effects of LPS on extinction and locomotion by using a lower dose of LPS (50μg/kg) which impaired locomotion without affecting extinction. In addition, 15h after an injection of 250μg/kg LPS in adult rats, extinction learning and recall were impaired without affecting locomotion. A sub-chronic treatment with candesartan, an angiotensin II type 1 receptor blocker, prevented the LPS-induced impairment of extinction in adult rats. Our results demonstrate that activation of the innate immune system can disrupt auditory fear extinction in adolescent and adult animals. These findings also provide direction for clinical studies of novel treatments that modulate the innate immune system for stress-related disorders like PTSD.

Preventive effects of ginsenoside Rg1 on post-traumatic stress disorder (PTSD)-like behavior in male C57/B6 mice

We investigated the preventive effects of Rg1 on a model of mouse post-traumatic stress disorder (PTSD) induced by electric shock combined with situation reminder and explored the underlying mechanism. In the experiment, before the PTSD animal model was developed, Rg1 (10, 5, and 2.5mg/kg) was orally administered for one week. After the animal model was established, PTSD-like behavior was observed using elevated plus maze, black and light box, and open field tests. One hour after the behavior test, all mice were sacrificed, and then serum corticosterone (CORT) and hypothalamus corticotrophin-releasing hormone (CRH) assays were performed. Results showed that Rg1 (5mg/kg) treatments relieved PTSD-like behavior by altering elevated serum corticosterone and hypothalamus CRH levels. By contrast, fluoxetine (3mg/kg) treatment reversed the behavior changes and had no effect on increased CORT and CRH levels. These findings confirmed the preventive effect of Rg1 in PTSD model. Decreasing CORT and CRH levels may be one of the underlying mechanisms.

Abstract 105: Increased Myocardial Sensitivity to Ischemic Injury in an Animal Model of Posttraumatic Stress Disorder

Background: Posttraumatic stress disorder (PTSD) is a psychological disorder characterized by the formation of traumatic memories following exposure to a life threatening event. In addition to psychological manifestations, PTSD promotes atherosclerosis and increases the incidence of myocardial infarction. However, it is unknown whether the effects of PTSD are limited to increasing the incidence of myocardial infarction or if PTSD also increases infarct severity. Therefore, we used an animal model of PTSD to determine whether posttraumatic stress influences infarct size and postischemic recovery of cardiac contractile function. Methods: Rats were subjected to a well-established animal model of PTSD that is based on predator exposure and psychosocial stress (Zoladz et al., Stress 11:259-281). Rats subjected to this model exhibit many PTSD-like characteristics including the formation of traumatic memories, increased anxiety, increased startle reflex, hypertension, and alterations in the hypothalamic-pituitary adrenal axis. Male rats (7 weeks of age) were either subjected to psychosocial stress (n = 9) or continuously housed in their home cages (n = 8) for 31 days. Hearts were subsequently isolated and subjected to 20 minutes of ischemia and 2 hours reperfusion on a Langendorff isolated heart system. Results: Stressed rats exhibited significantly elevated corticosterone concentrations and anxiety-like behavior in the elevated plus maze. Infarct sizes were significantly larger in hearts from stressed rats (44.7 ± 1.7 % of area at risk) compared to nonstressed rats (31.0 ± 5.4 % of area at risk). Consistent with increased myocardial injury, postischemic recovery of rate pressure product (stressed = 16,922 ± 1,554 mmHg*bpm; nonstressed = 26,407 ± 2,977 mmHg*bpm) and +dP/dT (stressed = 1,901 ± 189 mmHg/sec; nonstressed =3,259 ± 498 mmHg/sec) were significantly attenuated in hearts from stressed rats. Furthermore, postischemic end diastolic pressure was significantly elevated in hearts from stressed (57 ± 6 mmHg) compared to nonstressed (32 ± 7 mmHg) rats. Conclusion: This animal model suggests that PTSD may make the myocardium more sensitive to ischemic injury through a mechanism that is independent from its ability to promote atherosclerosis.

Dexamethasone Treatment Leads to Enhanced Fear Extinction and Dynamic Fkbp5 Regulation in Amygdala.

Posttraumatic stress disorder (PTSD) is both a prevalent and debilitating trauma-related disorder associated with dysregulated fear learning at the core of many of its signs and symptoms. Improvements in the currently available psychological and pharmacological treatments are needed in order to improve PTSD treatment outcomes and to prevent symptom relapse. In the present study, we used a putative animal model of PTSD that included presentation of immobilization stress (IMO) followed by fear conditioning (FC) a week later. We then investigated the acute effects of GR receptor activation on the extinction (EXT) of conditioned freezing, using dexamethasone administered systemically which is known to result in suppression of the HPA axis. In our previous work, IMO followed by tone-shock-mediated FC was associated with impaired fear EXT. In this study, we administered dexamethasone 4 h before EXT training and then examined EXT retention (RET) 24 h later to determine whether dexamethasone suppression rescued EXT deficits. Dexamethasone treatment produced dose-dependent enhancement of both EXT and RET. Dexamethasone was also associated with reduced amygdala Fkbp5 mRNA expression following EXT and after RET. Moreover, DNA methylation of the Fkbp5 gene occurred in a dose-dependent and time course-dependent manner within the amygdala. Additionally, we found dynamic changes in epigenetic regulation, including Dnmt and Tet gene pathways, as a function of both fear EXT and dexamethasone suppression of the HPA axis. Together, these data suggest that dexamethasone may serve to enhance EXT by altering Fkbp5-mediated glucocorticoid sensitivity via epigenetic regulation of Fkbp5 expression.

Long-lasting memory abnormalities following exposure to the mouse defense test battery: An animal model of PTSD

Memory dysfunctions are thought to play a crucial role both in the development and the maintenance of post-traumatic stress disorder (PTSD). Patients suffering from this condition persistently re-experience the traumatic event particularly when exposed to trauma-related cues and they display memory alterations. The objective of the present study was to investigate the long-term effects of a traumatic stress exposure on defensive behaviors and memory performance in mice confronted with a natural threat (i.e. a rat) in the defense test battery (MDTB), a procedure developed by the Blanchard group in the early nineties. The object recognition task, which addresses certain aspects of episodic memory, was used to assess the long-term consequences of stress on memory function. Mice were exposed to the MDTB followed two weeks later by a re-exposure to the test apparatus, but in the absence of the threat stimulus. Two hours after the second exposure to the MDTB apparatus, mice were exposed to the object recognition task (ORT). Another set of animals was used which were either exposed to the first or to the second MDTB session, before being tested in the ORT. Results showed that MDTB exposure produced long-lasting alterations in some defensive behaviors, such as escape attempts from the apparatus, which were increased during the re-exposure session at day 14 compared to non-exposed control mice. While exposure to the MDTB context only did not affect memory performance in the ORT, confrontation with the threat stimulus in the MDTB on day 1 impaired episodic memory two weeks after the stressful event. Finally, mice confronted both with the rat on day 1 and the MDTB context on day 14 displayed intact episodic memory performance in the ORT. We hypothesize that re-exposure to the context following a stressful event resulted in an increase of arousal, which subsequently led to an improvement in cognitive performance, a phenomenon also described in PTSD patients. The MDTB is a typical example of the tremendous efforts of Blanchard's lab to increase the translatability potential of the behavioral models of central nervous system disorders.

Environmental Enrichment Reduces Anxiety by Differentially Activating Serotonergic and Neuropeptide Y (NPY)-Ergic System in Indian Field Mouse (Mus booduga): An Animal Model of Post-Traumatic Stress Disorder.

Exposure to a predator elicits an innate fear response and mimics several behavioral disorders related to post-traumatic stress disorder (PTSD). The protective role of an enriched condition (EC) against psychogenic stressors in various animal models has been well documented. However, this condition has not been tested in field mice in the context of PTSD. In this study, we show that field mice (Mus booduga) housed under EC exhibit predominantly proactive and less reactive behavior compared with mice housed under standard conditions (SC) during exposure to their natural predator (field rat Rattus rattus). Furthermore, we observed that EC mice displayed less anxiety-like behavior in an elevated plus maze (EPM) and light/dark-box after exposure to the predator (7 hrs/7 days). In EC mice, predator exposure elevated the level of serotonin (5-Hydroxytrypamine, [5-HT]) in the amygdala as part of the coping response. Subsequently, the serotonin transporter (SERT) and 5-HT1A receptor were up-regulated significantly, but the same did not occur in the 5-HT2C receptor, which is associated with the activation of calmodulin-dependent protein kinase-II (CaMKII) and a transcription factor cAMP response element binding protein (CREB). Our results show that predator exposure induced the activation of CaMKII/CREB, which is accompanied with increased levels of histone acetylation (H3, H4) and decreased histone deacetylases (HDAC1, 2). Subsequently, in the amygdala, the transcription of brain-derived neurotrophic factor (BDNF), neuropeptide Y (NPY) and its Y1 receptor were up-regulated, whereas the Y2 receptor was down-regulated. Therefore, EC facilitated a coping response against a fear associated cue in a PTSD animal model and reduced anxiety by differentially activating serotonergic and NPY-ergic systems.

The Use of Thalidomide in Treating PTSD and Co‐morbid Pain in an Animal Model of PTSD

Single‐prolonged stress (SPS) is an established animal model for post‐traumatic stress disorder (PTSD). We have previously reported that SPS induces increases in serum TNF‐α levels as well as long‐lasting mechanical allodynia and thermal hyperalgesia at day 3 post SPS. The aim of this study was to determine the effects of TNF‐α blockade on development of PTSD and co‐morbid pain symptoms. To achieve this, male Sprague‐Dawley rats were subjected to SPS; half of the SPS and control group rats were immediately presented with 50 mg/kg thalidomide (THL), a potent TNF‐α blocker, in 10% DMSO vehicle, daily, i.p for 5 days; non‐SPS rats received vehicle injections. THL almost completely prevented mechanical allodynia and reduces thermal hyperalgesia associated with SPS (p<0.05) that is normally noted as early as day 3 post SPS, without altering baseline sensitivity itself. Using a 2‐way ANOVA, a significant interaction was observed between THL and SPS (p<0.0001). Additionally, utilizing the elevated plus maze test, THL treatment reduces anxiety like behaviors, specifically mobility time, immobility time, open entries and time spent in open arms (p<0.05). Also, using a 2‐way ANOVA, a significant interaction was observed between THL and SPS (p<0.05) This suggests that immunomodulatory drugs such as THL, may offer a novel therapeutic method to prevent or reduce symptoms of PTSD and co‐morbid pain if administered shortly after the traumatic event.SupportDepartment of the Army DMRDP W81XWH‐11‐2‐0077

β-Alanine supplemented diets enhance behavioral resilience to stress exposure in an animal model of PTSD.

This study investigated the effects of β-alanine (BA) ingestion on the behavioral and neuroendocrine response of post-traumatic stress disorder (PTSD) in a murine model. Animals were fed a normal diet with or without (PL) BA supplementation (100 mg kg−1) for 30 days. Animals were then exposed to a predator-scent stress (PSS) or a sham (UNEX). Behaviors were evaluated using an elevated plus maze (EPM) and acoustic startle response (ASR) 7 days following exposure to the PSS. Corticosterone concentrations (CS), expression of brain-derived neurotrophic factor (BDNF), and brain carnosine concentrations were analyzed a day later. Animals in PSS+PL spent significantly less time in the open arms and in the number of entries in the EPM than PSS+BA, UNEX+BA, or UNEX+PL. Animals in PSS+BA had comparable scores to UNEX+BA. Anxiety index was higher (p < 0.05) in PSS+PL compared to PSS+BA or animals that were unexposed. ASR and freezing were greater (p < 0.05) in animals exposed to PSS compared to animals unexposed. CS expression was higher (p < 0.05) in animals exposed to PSS compared to unexposed animals. Brain carnosine concentrations in the hippocampus and other brain sections were significantly greater in animals supplemented with BA compared to PL. BDNF expression in the CA1 and DG subregions of the hippocampus was lower (p < 0.05) in animals exposed and fed a normal diet compared to animals exposed and supplemented with BA, or animals unexposed. In conclusion, BA supplementation in rats increased brain carnosine concentrations and resulted in a reduction in PTSD-like behavior, which may be mediated in part by maintaining BDNF expression in the hippocampus.

Effects of fluoxetine on the amygdala and the hippocampus after administration of a single prolonged stress to male Wistar rates: In vivo proton magnetic resonance spectroscopy findings

Posttraumatic stress disorder (PTSD) is an anxiety- and memory-based disorder. The hippocampus and amygdala are key areas in mood regulation. Fluoxetine was found to improve the anxiety-related symptoms of PTSD patients. However, little work has directly examined the effects of fluoxetine on the hippocampus and the amygdala. In the present study, male Wistar rats received fluoxetine or vehicle after exposure to a single prolonged stress (SPS), an animal model of PTSD. In vivo proton magnetic resonance spectroscopy (1H-MRS) was performed −1, 1, 4, 7 and 14 days after SPS to examine the effects of fluoxetine on neurometabolite changes in amygdala, hippocampus and thalamus. SPS increased the N-acetylaspartate (NAA)/creatine (Cr) and choline moieties (Cho)/Cr ratios in the bilateral amygdala on day 4, decreased the NAA/Cr ratio in the left hippocampus on day 1, and increased both ratios in the right hippocampus on day 14. But no significant change was found in the thalamus. Fluoxetine treatment corrected the SPS increases in the NAA/Cr and Cho/Cr levels in the amygdala on day 4 and in the hippocampus on day 14, but it failed to normalise SPS-associated decreases in NAA/Cr levels in the left hippocampus on day 1. These results suggested that metabolic abnormalities in the amygdala and the hippocampus were involved in SPS, and different effects of fluoxetine in correcting SPS-induced neurometabolite changes among the three areas. These findings have implications for fluoxetine treatment in PTSD.

Risperidone Attenuates Modified Stress-Re-stress Paradigm-Induced Mitochondrial Dysfunction and Apoptosis in Rats Exhibiting Post-traumatic Stress Disorder-Like Symptoms.

Mitochondria play a significant role in the pathophysiology of post-traumatic stress disorder (PTSD). Risperidone and paroxetine were evaluated for their effect on mitochondrial dysfunction and mitochondria-dependent apoptosis in discrete brain regions in modified stress re-stress (SRS) animal model of PTSD. Male rats were subjected to stress protocol of 2 h restraint and 20 min forced swim followed by halothane anesthesia on day 2 (D-2). Thereafter, rats were exposed to re-stress (forced swim) on D-8 and at 6-day intervals on D-14, D-20, D-26, and D-32. The rats were treated with risperidone (0.01, 0.1, and 1.0 mg/kg p.o.) and paroxetine (10.0 mg/kg p.o.) from D-8 to D-32. Risperidone at median dose and paroxetine ameliorated modified SRS-induced depressive-like symptom (increase in immobility period) in forced swim, anxiety-like behavior (decrease in percentage of open arm entries and time spent) in elevated plus maze and cognitive deficits (loss in spatial recognition memory) in Y-maze tests on D-32. Risperidone, but not paroxetine, attenuated modified SRS-induced decreases in plasma corticosterone levels. Risperidone ameliorated increase in the activity of mitochondrial respiratory complex (I, II, IV, and V), decreases in the levels of mitochondrial membrane potential, cytochrome-C and caspase-9 in the hippocampus, hypothalamus, pre-frontal cortex, and amygdala. However, both drugs attenuated modified SRS-induced increase in the number of apoptotic cells and caspase-3 levels in all the brain regions indicating anti-apoptotic activity of these drugs. Hence, these results suggest that anti-apoptotic activity could be a common mechanism for anti-PTSD-like effect irrespective of the pathways of apoptosis in the modified SRS model.

Sex differences in the single prolonged stress model

Post traumatic stress disorder (PTSD) is a debilitating anxiety disorder resulting from traumatic stress exposure. Females are more likely to develop PTSD than males, but neurobiological mechanisms underlying female susceptibility are lacking. This can be addressed by using nonhuman animal models. Single prolonged stress (SPS), a nonhuman animal model of PTSD, results in cued fear extinction retention deficits and hippocampal glucocorticoid receptor (GR) upregulation in male rats. These effects appear linked in the SPS model, as well as in PTSD. However, the effects of SPS on cued fear extinction retention and hippocampal GRs in female rats remain unknown. Thus, we examined sex differences in SPS-induced cued fear extinction retention deficits and hippocampal GR upregulation. SPS induced cued fear extinction retention deficits in male rats but not female rats. SPS enhanced GR levels in the dorsal hippocampus of female rats, but not male rats. SPS had no effects on ventral hippocampal GR levels, but ventral hippocampal GR levels were attenuated in female rats relative to males. These results suggest that female rats are more resilient to the effects of SPS. The results also suggest that GR upregulation and cued fear extinction retention deficits can be dissociated in the SPS model.