Response variation following trauma: a translational neuroscience approach to understanding PTSD

A critical role for protein tyrosine phosphatase nonreceptor type 5 in determining individual susceptibility to develop stress-related cognitive and morphological changes

While stressful life events confer increased risk for the development of psychopathology, most individuals experiencing adversity maintain normal psychological functioning, suggesting that individual differences may influence the susceptibility to develop stress-related psychiatric disorders. However, little is known about what determines this difference between individuals at the molecular level. In the present study, we identify that protein tyrosine phosphatase nonreceptor type 5 (PTPN5) (also known as STEP) is a critical determinant of differences in individual susceptibility to develop stress-related cognitive and morphological changes in rats. Our data demonstrate that ablation of PTPN5 expression delays physiological recovery from stress and augments the development of stress-related cognitive and morphological changes, whereas overexpression of a constitutively active variant of PTPN5 enhances the individual's resilience to stress. Our data also reveal that reduced PTPN5 expression prolongs the duration of extracellular signal-regulated kinase activation, leading to an elevation of Ca(V)1.2 channel expression and a recovery delay of K(V)4.2 channels from inactivation, which in turn heightens neuronal vulnerability to glutamate toxicity. Moreover, intraperitoneal injections of L-type Ca(2+) channel blocker nifedipine after stress resulted in a significantly lower rate for developing stress-related cognitive and morphological changes seen in PTPN5 knockdown rats. Together, these results identify a novel role for PTPN5 in mediating the development of stress-related cognitive and morphological changes and suggest that people with PTPN5 deficiency may have a greater susceptibility to capture the deleterious effects of stress.

Can traumatic stress alter the brain? Understanding the implications of early trauma on brain development and learning

BACKGROUND

Youth who experience traumatic stress and develop post-traumatic symptoms secrete higher levels of the glucocorticoid cortisol than youth with no trauma history. Animal research suggests that excess corticosterone secretion can lead to neurotoxicity in areas of the brain rich in glucocorticoid receptors such as the hippocampus and the prefrontal cortex (PFC). These two areas of the brain are involved in memory processing and executive function, both critical functions of learning.

METHODS

In this article, we summarize findings presented at the National Summit for Stress and the Brain conducted at Johns Hopkins University's Department of Public Health in April 2011. The presentation highlighted structural and functional imaging findings in the hippocampus and PFC of youth with post-traumatic stress symptoms (PTSS).

RESULTS

Youth with PTSS have higher levels of cortisol. Prebedtime cortisol levels predict decreases in hippocampal volume longitudinally. Cortisol levels are negatively correlated with volume in the PFC. Functional imaging studies demonstrate reduced hippocampal and PFC activities on tasks of memory and executive function in youth with PTSS when compared with control subjects.

CONCLUSIONS

Effective interventions for youth with PTSS should target improved function of frontolimbic networks. Treatment outcome research using these potential markers can help develop more focused interventions that target the impaired learning of vulnerable youth experiencing traumatic stress.

Targeting memory processes with drugs to prevent or cure PTSD

INTRODUCTION

Post-traumatic stress disorder (PTSD) is a chronic debilitating psychiatric disorder resulting from exposure to a severe traumatic stressor and an area of great unmet medical need. Advances in pharmacological treatments beyond the currently approved SSRIs are needed.

AREAS COVERED

Background on PTSD, as well as the neurobiology of stress responding and fear conditioning, is provided. Clinical and preclinical data for investigational agents with diverse pharmacological mechanisms are summarized.

EXPERT OPINION

Advances in the understanding of stress biology and mechanisms of fear conditioning plasticity provide a rationale for treatment approaches that may reduce hyperarousal and dysfunctional aversive memories in PTSD. One challenge is to determine if these components are independent or reflect a common underlying neurobiological alteration. Numerous agents reviewed have potential for reducing PTSD core symptoms or targeted symptoms in chronic PTSD. Promising early data support drug approaches that seek to disrupt dysfunctional aversive memories by interfering with consolidation soon after trauma exposure, or in chronic PTSD, by blocking reconsolidation and/or enhancing extinction. Challenges remain for achieving selectivity when attempting to alter aversive memories. Targeting the underlying traumatic memory with a combination of pharmacological therapies applied with appropriate chronicity, and in combination with psychotherapy, is expected to substantially improve PTSD treatment.

Relations among posttraumatic stress disorder, comorbid major depression, and HPA function: a systematic review and meta-analysis

Exposure to traumatic stress is associated with increased risk for posttraumatic stress disorder (PTSD) and alterations of hypothalamic-pituitary-adrenocortical (HPA) function. Research linking traumatic stress with HPA function in PTSD has been inconsistent, however, in part due to (a) the inclusion of trauma-exposed individuals without PTSD (TE) in control groups and (b) a failure to consider comorbid major depressive disorder (MDD) and moderating variables. This meta-analysis of 47 studies (123 effect sizes, N=6008 individuals) revealed that daily cortisol output was lower for PTSD (d=-.36, SE=.15, p=.008) and PTSD+MDD (d=-.65, SE=.25, p=.008) groups relative to no trauma controls (NTC); TE and NTC groups did not differ significantly from each other. Afternoon/evening cortisol was lower in TE (d=-.25, SE=.09, p=.007) and PTSD (d=-.27, SE=.12, p=.021) groups and higher in PTSD+MDD groups (d=.49, SE=.24, p=.041) relative to NTC. Post-DST cortisol levels were lower in PTSD (d=-.40, SE=.12, p<.001), PTSD+MDD (d=-.65, SE=.14, p<.001), and TE groups (d=-.53, SE=.14, p<.001) relative to NTC. HPA effect sizes were moderated by age, sex, time since index event, and developmental timing of trauma exposure. These findings suggest that enhanced HPA feedback function may be a marker of trauma-exposure rather than a specific mechanism of vulnerability for PTSD, whereas lower daily cortisol output may be associated with PTSD in particular.

Complex PTSD is on the trauma spectrum: comment on Resick et al. (2012)

Conceptualizing posttraumatic stress disorder (PTSD) along a spectrum with complex and simple features is integrative and models an approach taken by disciplines in medicine outside of psychiatry. This perspective is offered in the Resick et al. (2012) review. To best delineate the nature and permeability of the border between Complex PTSD and PTSD, an emphasis on clarifying underlying biological processes is needed to move beyond our current reliance on symptomatic description.

Photoperiod alters fear responses and basolateral amygdala neuronal spine density in white-footed mice (Peromyscus leucopus)

Photoperiodism is a biological phenomenon in which environmental day length is monitored to ascertain time of year to engage in seasonally appropriate adaptations. This trait is common among organisms living outside of the tropics. White-footed mice (Peromyscus leucopus) are small photoperiodic rodents which display a suite of adaptive responses to short day lengths, including reduced hippocampal volume, impairments in hippocampal-mediated memory, and enhanced hypothalamic-pituitary-adrenal axis reactivity. Because these photoperiodic changes in brain and behavior mirror some of the etiology of post-traumatic stress disorder (PTSD), we hypothesized that photoperiod may also alter fear memory and neuronal morphology within the hippocampus-basolateral amygdala-prefrontal cortex fear circuit. Ten weeks of exposure to short days increased fear memory in an auditory-cued fear conditioning test. Short days also increased dendritic spine density of the neurons of the basolateral amygdala, without affecting morphology of pyramidal neurons within the infralimbic region of the medial prefrontal cortex. Taken together, photoperiodic phenotypic changes in brain morphology and physiology induced by a single environmental factor, exposure to short day lengths, affect responses to fearful stimuli in white-footed mice. These results have potential implications for understanding seasonal changes in fear responsiveness, as well as for expanding translational animal models for studying gene-environment interactions underlying psychiatric diseases, such as PTSD.

Genetic strain differences in learned fear inhibition associated with variation in neuroendocrine, autonomic, and amygdala dendritic phenotypes

Mood and anxiety disorders develop in some but not all individuals following exposure to stress and psychological trauma. However, the factors underlying individual differences in risk and resilience for these disorders, including genetic variation, remain to be determined. Isogenic inbred mouse strains provide a valuable approach to elucidating these factors. Here, we performed a comprehensive examination of the extinction-impaired 129S1/SvImJ (S1) inbred mouse strain for multiple behavioral, autonomic, neuroendocrine, and corticolimbic neuronal morphology phenotypes. We found that S1 exhibited fear overgeneralization to ambiguous contexts and cues, impaired context extinction and impaired safety learning, relative to the (good-extinguishing) C57BL/6J (B6) strain. Fear overgeneralization and impaired extinction was rescued by treatment with the front-line anxiety medication fluoxetine. Telemetric measurement of electrocardiogram signals demonstrated autonomic disturbances in S1 including poor recovery of fear-induced suppression of heart rate variability. S1 with a history of chronic restraint stress displayed an attenuated corticosterone (CORT) response to a novel, swim stressor. Conversely, previously stress-naive S1 showed exaggerated CORT responses to acute restraint stress or extinction training, insensitivity to dexamethasone challenge, and reduced hippocampal CA3 glucocorticoid receptor mRNA, suggesting downregulation of negative feedback control of the hypothalamic-pituitary-adrenal axis. Analysis of neuronal morphology in key neural nodes within the fear and extinction circuit revealed enlarged dendritic arbors in basolateral amygdala neurons in S1, but normal infralimbic cortex and prelimbic cortex dendritic arborization. Collectively, these data provide convergent support for the utility of the S1 strain as a tractable model for elucidating the neural, molecular and genetic basis of persistent, excessive fear.

Neural Regulation of the Stress Response: The Many Faces of Feedback

The mammalian stress response is an integrated physiological and psychological reaction to real or perceived adversity. Glucocorticoids (GCs) are an important component of this response, acting to redistribute energy resources to both optimize survival in the face of challenge and restore homeostasis after the immediate threat has subsided. Release of GCs is mediated by the hypothalamo-pituitary-adrenocortical (HPA) axis, driven by a neural signal originating in the paraventricular nucleus (PVN). Stress levels of GCs bind to glucocorticoid receptors (GRs) in multiple body compartments, including brain, and consequently have wide-reaching actions. For this reason, GCs serve a vital function in feedback inhibition of their own secretion. Fast, non-genomic feedback inhibition of the HPA axis is mediated at least in part by GC signaling in the PVN, acting by a cannabinoid-dependent mechanism to rapidly reduce both neural activity and GC release. Delayed feedback termination of the HPA axis response is mediated by forebrain GRs, presumably by genomic mechanisms. GCs also act in the brainstem to attenuate neuropeptidergic excitatory input to the PVN via acceleration of mRNA degradation, providing a mechanism to attenuate future responses to stressors. Thus, rather than having a single defined feedback switch, GCs work through multiple neurocircuits and signaling mechanisms to coordinate HPA axis activity to suit the overall needs of multiple body systems.

Consolidation of remote fear memories involves Corticotropin-Releasing Hormone (CRH) receptor type 1-mediated enhancement of AMPA receptor GluR1 signaling in the dentate gyrus

Persistent dreadful memories and hyperarousal constitute prominent psychopathological features of posttraumatic stress disorder (PTSD). Here, we used a contextual fear conditioning paradigm to demonstrate that conditional genetic deletion of corticotropin-releasing hormone (CRH) receptor 1 within the limbic forebrain in mice significantly reduced remote, but not recent, associative and non-associative fear memories. Per os treatment with the selective CRHR1 antagonist DMP696 (3 mg/kg) attenuated consolidation of remote fear memories, without affecting their expression and retention. This could be achieved, if DMP696 was administered for 1 week starting as late as 24 h after foot shock. Furthermore, by combining electrophysiological recordings and western blot analyses, we demonstrate a delayed-onset and long-lasting increase in AMPA receptor (AMPAR) GluR1-mediated signaling in the dentate gyrus (DG) of the dorsal hippocampus 1 month after foot shock. These changes were absent from CRHR1-deficient mice and after DMP696 treatment. Inactivation of hippocampal GluR1-containing AMPARs by antisense oligonucleotides or philantotoxin 433 confirmed the behavioral relevance of AMPA-type glutamatergic neurotransmission in maintaining the high levels of remote fear in shocked mice with intact CRHR1 signaling. We conclude that limbic CRHR1 receptors enhance the consolidation of remote fear memories in the first week after foot shock by increasing the expression of Ca(2+)-permeable GluR1-containing AMPARs in the DG. These findings suggest both receptors as rational targets for the prevention and therapy, respectively, of psychopathology associated with exaggerated fear memories, such as PTSD.

DNA methylation in repetitive elements and post-traumatic stress disorder: a case-control study of US military service members

AIM

We investigated serum DNA methylation patterns in genomic repetitive elements, LINE-1 and Alu, for post-traumatic stress disorder (PTSD) cases and controls who were US military service members recently deployed to Afghanistan or Iraq.

METHODS

Cases (n = 75) had a postdeployment diagnosis of PTSD. Controls (n = 75) were randomly selected service members with no postdeployment PTSD diagnosis. Pre- and post-deployment sera were accessed, DNA was extracted and DNA methylation (percentage 5-methyl cytosine) was quantified via pyrosequencing. Conditional and unconditional logistic regressions were used to compare: cases post- to pre-deployment; controls post- to pre-deployment; cases to controls predeployment; cases to controls postdeployment.

RESULTS

LINE-1 was hypermethylated in controls post- versus pre-deployment (odds ratio [OR]: 1.33; 95% CI: 1.06-1.65) and hypomethylated in cases versus controls postdeployment (OR: 0.82; 95% CI: 0.67-1.01). Alu was hypermethylated for cases versus controls predeployment (OR: 1.46; 95% CI: 1.08-1.97).

CONCLUSION

Patterns of hypermethylation of LINE-1 in controls postdeployment and of Alu in cases postdeployment are intriguing and may suggest resilience or vulnerability factors.

Single prolonged stress disrupts retention of extinguished fear in rats

Clinical research has linked post-traumatic stress disorder (PTSD) with deficits in fear extinction. However, it is not clear whether these deficits result from stress-related changes in the acquisition or retention of extinction or in the regulation of extinction memories by context, for example. In this study, we used the single prolonged stress (SPS) animal model of PTSD and fear conditioning procedures to examine the effects of prior traumatic stress on the acquisition, retention, and context-specificity of extinction. SPS administered one week prior to fear conditioning had no effect on the acquisition of fear conditioning or extinction but disrupted the retention of extinction memories for both contextual and cued fear. This SPS effect required a post-stress incubation period to manifest. The results demonstrate that SPS disrupts extinction retention, leading to enhanced fear renewal; further research is needed to identify the neurobiological processes through which SPS induces these effects.

Fear erasure in mice requires synergy between antidepressant drugs and extinction training

Antidepressant drugs and psychotherapy combined are more effective in treating mood disorders than either treatment alone, but the neurobiological basis of this interaction is unknown. To investigate how antidepressants influence the response of mood-related systems to behavioral experience, we used a fear-conditioning and extinction paradigm in mice. Combining extinction training with chronic fluoxetine, but neither treatment alone, induced an enduring loss of conditioned fear memory in adult animals. Fluoxetine treatment increased synaptic plasticity, converted the fear memory circuitry to a more immature state, and acted through local brain-derived neurotrophic factor. Fluoxetine-induced plasticity may allow fear erasure by extinction-guided remodeling of the memory circuitry. Thus, the pharmacological effects of antidepressants need to be combined with psychological rehabilitation to reorganize networks rendered more plastic by the drug treatment.

Classical conditioning and conditioning-specific reflex modification of rabbit heart rate as a function of unconditioned stimulus location

Heart rate conditioning is used as an index of conditioned fear and is important for understanding disorders of anxiety and stress, including post traumatic stress disorder (PTSD). One important feature of PTSD is that patients generalize conditioned fear from danger signals to safety signals especially when the two signals have overlapping features. What has not been determined is whether generalization occurs between unconditioned stimuli with overlapping features. In the current experiment, heart rate conditioning and conditioning-specific reflex modification of rabbit heart rate were examined as a function of two different unconditioned stimulus locations. Heart rate conditioning occurred at identical terminal levels whether electrical stimulation was presented near the eye or on the back. Despite different heart rate response topographies to electrical stimulation at the two locations, conditioning-specific reflex modification was detected near the eye and on the back and appeared to generalize between the locations. Interestingly, only conditioning-specific reflex modification detected on the back persisted for a week after heart rate conditioning. This persistence may be a model for some features of post traumatic stress disorder. Overgeneralization of unconditioned responses to unconditioned stimuli similar to the trauma may also be an important aspect of PTSD modeled here.

Post-traumatic stress disorder: the neurobiological impact of psychological trauma

The classic fight-or-flight response to perceived threat is a reflexive nervous phenomenon thai has obvious survival advantages in evolutionary terms. However, the systems that organize the constellation of reflexive survival behaviors following exposure to perceived threat can under some circumstances become dysregulated in the process. Chronic dysregulation of these systems can lead to functional impairment in certain individuals who become “psychologically traumatized” and suffer from post-traumatic stress disorder (PTSD), A body of data accumulated over several decades has demonstrated neurobiological abnormalities in PTSD patients. Some of these findings offer insight into the pathophysiology of PTSD as well as the biological vulnerability of certain populations to develop PTSD, Several pathological features found in PTSD patients overlap with features found in patients with traumatic brain injury paralleling the shared signs and symptoms of these clinical syndromes.

Incubation of conditioning-specific reflex modification: implications for Post Traumatic Stress Disorder

Incubation of fear has been used to account for the delayed manifestation of symptoms of fear and anxiety including the delayed onset of Post Traumatic Stress Disorder (PTSD). We have shown the utility of classical conditioning-specific modification of the rabbit nictitating membrane response (NMR) as a model of PTSD. This modification includes an exaggeration in the size and a change in the timing of the unconditioned NMR after several days of classical conditioning. To assess the effects of incubation on conditioning-specific modification, we measured changes in responding as a function of the time between classical conditioning and NMR testing. After just one day of classical conditioning resulting in modest levels of learning, increases in response size were an inverted-U shaped function of days of incubation with little if any change occurring one and ten days after training but significant change occurring after six days. The incubation effect persisted for a week. An unpaired control group showed no change in the size of the response confirming the incubation effect was associative. The results bear a striking resemblance to symptoms of PTSD that do not always occur immediately after trauma and become exacerbated over time and then persist. They point to a window when incubation can exacerbate symptoms and speak to the vulnerability of re-experiencing trauma too soon. This could be a serious problem for military or emergency personnel recalled to combat or a disaster site without sufficient time to deal with the effects of their initial experiences.

Stress-induced enhancement of fear conditioning and sensitization facilitates extinction-resistant and habituation-resistant fear behaviors in a novel animal model of posttraumatic stress disorder

Posttraumatic stress disorder (PTSD) is characterized by stress-induced symptoms including exaggerated fear memories, hypervigilance and hyperarousal. However, we are unaware of an animal model that investigates these hallmarks of PTSD especially in relation to fear extinction and habituation. Therefore, to develop a valid animal model of PTSD, we exposed rats to different intensities of footshock stress to determine their effects on either auditory predator odor fear extinction or habituation of fear sensitization. In Experiment 1, rats were exposed to acute footshock stress (no shock control, 0.4 mA, or 0.8 mA) immediately prior to auditory fear conditioning training involving the pairing of auditory clicks with a cloth containing cat odor. When presented to the conditioned auditory clicks in the next 5 days of extinction testing conducted in a runway apparatus with a hide box, rats in the two shock groups engaged in higher levels of freezing and head out vigilance-like behavior from the hide box than the no shock control group. This increase in fear behavior during extinction testing was likely due to auditory activation of the conditioned fear state because Experiment 2 demonstrated that conditioned fear behavior was not broadly increased in the absence of the conditioned auditory stimulus. Experiment 3 was then conducted to determine whether acute exposure to stress induces a habituation resistant sensitized fear state. We found that rats exposed to 0.8 mA footshock stress and subsequently tested for 5 days in the runway hide box apparatus with presentations of nonassociative auditory clicks exhibited high initial levels of freezing, followed by head out behavior and culminating in the occurrence of locomotor hyperactivity. In addition, Experiment 4 indicated that without delivery of nonassociative auditory clicks, 0.8 mA footshock stressed rats did not exhibit robust increases in sensitized freezing and locomotor hyperactivity, albeit head out vigilance-like behavior continued to be observed. In summary, our animal model provides novel information on the effects of different intensities of footshock stress, auditory-predator odor fear conditioning, and their interactions on facilitating either extinction-resistant or habituation-resistant fear-related behavior. These results lay the foundation for exciting new investigations of the hallmarks of PTSD that include the stress-induced formation and persistence of traumatic memories and sensitized fear.

Early fear as a predictor of avoidance in a rat model of post-traumatic stress disorder

Exposure of humans and animals to an intensely fearful experience can lead to an enduring behavioral profile involving fear and avoidance. The present study examined if rats that show more fear to a novel tone one day after exposure to footshocks exhibit more avoidance-like responses over a 4-week period. Rats were exposed to an episode of moderately intense footshock (5×2s episodes of 1.5mA presented randomly over 3min). Shock rats that exhibited a high level of fear (HR) to a novel tone one day after the shock exposure showed more avoidance of open spaces and novel rats when compared to shock rats that exhibited a lower level of fear to the novel tone (LR). Similarly, HR emitted more ultrasonic vocalization in the dysphoric range (20-30kHz) when placed in a novel chamber or the chamber in which shock was given. This study highlights the importance of early fear as a contributing factor for the development of lasting changes in avoidance. These results also support the view that the presence of an intense peritraumatic stress response may be a predictor of the subsequent development of a lasting negative emotional state in humans exposed to trauma.

Interplay of amygdala and cingulate plasticity in emotional fear

The amygdala is known to be a critical brain region for emotional fear. It is believed that synaptic plasticity within the amygdala is the cellular basis of fear memory. Recent studies demonstrate that cortical areas such as the prefrontal cortex (PFC) and anterior cingulate cortex (ACC) may also contribute to the formation of fear memory, including trace fear memory and remote fear memory. At synaptic level, fear conditioning also triggers plastic changes within the cortical areas immediately after the condition. These results raise the possibility that certain forms of synaptic plasticity may occur within the cortex while synaptic potentiation takes place within synapses in the hippocampus and amygdala. This hypothesis is supported by electrophysiological evidence obtained from freely moving animals that neurons in the hippocampus/amygdala fire synchronous activities with cortical neurons during the learning. To study fear-related synaptic plasticity in the cortex and its functional connectivity with neurons in the amygdala and hippocampus will help us understand brain mechanisms of fear and improve clinical treatment of emotional disorders in patients.

Pharmacological modulation of stress-induced behavioral changes in the light/dark exploration test in male C57BL/6J mice

Psychological stress is a major risk factor for mood and anxiety disorders. However, the phenotypic manifestation of stress effects varies across individuals, likely due, in part, to genetic variation. Modeling the behavioral and neural consequences of stress across genetically diverse inbred mouse strains is a valuable approach to studying gene × stress interactions. Recent work has shown that C57BL/6J mice exposed to ten daily sessions of restraint stress exhibited increased exploration of the aversive light compartment in the light/dark exploration (LDE) test. Here we sought to clarify the nature of this stress-induced phenotype by testing the ability of treatment with various clinically efficacious drugs of different therapeutic classes to rescue it. Ten days of restraint increased light compartment exploration, reduced body weight and sensitized the corticosterone response to swim stress. Subchronic administration (during stress and LDE testing) of fluoxetine, and to a lesser extent, lithium chloride, rescued stress-induced LDE behavior. Chronic fluoxetine treatment prior to (plus during stress and testing) failed to block the LDE stress effect. Acute administration of antipsychotic haloperidol, anti-ADHD medication methylphenidate or anxiolytic drug chlordiazepoxide, prior to LDE testing, was also unable to normalize the LDE stress effect. Collectively, these data demonstrate a treatment-selective prophylactic rescue of a restraint stress-induced behavioral abnormality in the C57BL/6J inbred strain. Further work with this novel model could help elucidate genetic and neural mechanisms mediating stress-induced changes in mouse 'emotion-relevant' behaviors and, ultimately, further understanding of the pathophysiology of stress-related neuropsychiatric disorders. This article is part of a Special Issue entitled 'Anxiety and Depression'.

Stress risk factors and stress-related pathology: neuroplasticity, epigenetics and endophenotypes

This paper highlights a symposium on stress risk factors and stress susceptibility, presented at the Neurobiology of Stress workshop in Boulder, CO, in June 2010. This symposium addressed factors linking stress plasticity and reactivity to stress pathology in animal models and in humans. Dr. J. Radley discussed studies demonstrating prefrontal cortical neuroplasticity and prefrontal control of hypothalamo-pituitary-adrenocortical axis function in rats, highlighting the emerging evidence of the critical role that this region plays in normal and pathological stress integration. Dr. M. Kabbaj summarized his studies of possible epigenetic mechanisms underlying behavioral differences in rat populations bred for differential stress reactivity. Dr. L. Jacobson described studies using a mouse model to explore the diverse actions of antidepressants in brain, suggesting mechanisms whereby antidepressants may be differentially effective in treating specific depression endophenotypes. Dr. R. Yehuda discussed the role of glucocorticoids in post-traumatic stress disorder (PTSD), indicating that low cortisol level may be a trait that predisposes the individual to development of the disorder. Furthermore, she presented evidence indicating that traumatic events can have transgenerational impact on cortisol reactivity and development of PTSD symptoms. Together, the symposium highlighted emerging themes regarding the role of brain reorganization, individual differences, and epigenetics in determining stress plasticity and pathology.

Childhood trauma associated with short leukocyte telomere length in posttraumatic stress disorder

BACKGROUND

Posttraumatic stress disorder (PTSD) is associated with increased risk for age-related diseases and early mortality. An accelerated rate of biological aging could contribute to this increased risk. To investigate, we assessed leukocyte telomere length (LTL), an emerging marker of biological age, in men and women with and without PTSD. We also examined childhood trauma, a risk factor for both PTSD and short LTL, as a potential contributor to short LTL in PTSD.

METHODS

Participants included 43 adults with chronic PTSD (n = 18 with multiple categories of childhood trauma) and 47 control subjects (none with multiple categories of childhood trauma) (mean age = 30.55, SD = 7.44). Exclusion criteria included physical illness, medication use, obesity, alcohol or substance abuse, and pregnancy. Structured clinical interviews were conducted to assess PTSD and other psychiatric disorders and childhood trauma exposure. LTL was measured with a quantitative polymerase chain reaction method.

RESULTS

As predicted, participants with PTSD had shorter age-adjusted LTL than control subjects. Exposure to childhood trauma was also associated with short LTL. In fact, childhood trauma seemed to account for the PTSD group difference in LTL; only participants with PTSD and exposure to multiple categories of childhood trauma had significantly shorter LTL than control subjects.

CONCLUSIONS

Childhood trauma is associated with short LTL in individuals with PTSD. Chronic exposure to the psychobiological sequelae of childhood trauma could increase risk for PTSD and short LTL. Thus, the lasting psychological impact of exposure to trauma in childhood might be accompanied by equally enduring changes at the molecular level.

Disruption of the neuregulin 1 gene in the rat alters HPA axis activity and behavioral responses to environmental stimuli

Exposure to stress can result in an increased risk for psychiatric disorders, especially among genetically predisposed individuals. Neuregulin 1 (NRG1) is a susceptibility gene for schizophrenia and is also associated with psychotic bipolar disorder. In the rat, the neurons of the hypothalamic paraventricular nucleus show strong expression of Nrg1 mRNA. In patients with schizophrenia, a single nucleotide polymorphism in the 5' region of NRG1 interacts with psychosocial stress to affect reactivity to expressed emotion. However, there is virtually no information on the role of NRG1 in hypothalamic-pituitary-adrenal axis function, and whether the protein is expressed in the paraventricular nucleus is unknown. The present studies utilize a unique line of Nrg1 hypomorphic rats (Nrg1(Tn)) generated by gene trapping with the Sleeping Beauty transposon. We first established that the Nrg1(Tn) rats displayed reduced expression of both the mRNA and protein corresponding to the Type II NRG1 isoform. After confirming, using wild type animals, that Type II NRG1 is expressed in the neurocircuitry involved in regulating hypothalamic-pituitary-adrenal axis responses to environmental stimuli, the Nrg1(Tn) rats were then used to test the hypothesis that altered expression of Type II NRG1 disrupts stress regulation and reactivity. In support of this hypothesis, Nrg1(Tn) rats have disrupted basal and acute stress recovery corticosterone secretion, differential changes in expression of glucocorticoid receptors in the pituitary, paraventricular nucleus and hippocampus, and a failure to habituate to an open field. Together, these findings point to NRG1 as a potential novel regulator of neuroendocrine responses to stress as well as behavioral reactivity.

Fear conditioning, synaptic plasticity and the amygdala: implications for posttraumatic stress disorder

Posttraumatic stress disorder (PTSD) is an anxiety disorder that can develop after a traumatic experience such as domestic violence, natural disasters or combat-related trauma. The cost of such disorders on society and the individual can be tremendous. In this article, we review how the neural circuitry implicated in PTSD in humans is related to the neural circuitry of fear. We then discuss how fear conditioning is a suitable model for studying the molecular mechanisms of the fear components that underlie PTSD, and the biology of fear conditioning with a particular focus on the brain-derived neurotrophic factor (BDNF)-tyrosine kinase B (TrkB), GABAergic and glutamatergic ligand-receptor systems. We then summarize how such approaches might help to inform our understanding of PTSD and other stress-related disorders and provide insight to new pharmacological avenues of treatment of PTSD.

Epigenetic modification of hippocampal Bdnf DNA in adult rats in an animal model of post-traumatic stress disorder

Epigenetic alterations of the brain-derived neurotrophic factor (Bdnf) gene have been linked with memory, stress, and neuropsychiatric disorders. Here we examined whether there was a link between an established rat model of post-traumatic stress disorder (PTSD) and Bdnf DNA methylation. Adult male Sprague-Dawley rats were given psychosocial stress composed of two acute cat exposures in conjunction with 31 days of daily social instability. These manipulations have been shown previously to produce physiological and behavioral sequelae in rats that are comparable to symptoms observed in traumatized people with PTSD. We then assessed Bdnf DNA methylation patterns (at exon IV) and gene expression. We have found here that the psychosocial stress regimen significantly increased Bdnf DNA methylation in the dorsal hippocampus, with the most robust hypermethylation detected in the dorsal CA1 subregion. Conversely, the psychosocial stress regimen significantly decreased methylation in the ventral hippocampus (CA3). No changes in Bdnf DNA methylation were detected in the medial prefrontal cortex or basolateral amygdala. In addition, there were decreased levels of Bdnf mRNA in both the dorsal and ventral CA1. These results provide evidence that traumatic stress occurring in adulthood can induce CNS gene methylation, and specifically, support the hypothesis that epigenetic marking of the Bdnf gene may underlie hippocampal dysfunction in response to traumatic stress. Furthermore, this work provides support for the speculative notion that altered hippocampal Bdnf DNA methylation is a cellular mechanism underlying the persistent cognitive deficits which are prominent features of the pathophysiology of PTSD.

The emotional Stroop task and posttraumatic stress disorder: a meta-analysis

Posttraumatic stress disorder (PTSD) is associated with significant impairment and lowered quality of life. The emotional Stroop task (EST) has been one means of elucidating some of the core deficits in PTSD, but this literature has remained inconsistent. We conducted a meta-analysis of EST studies in PTSD populations in order to synthesize this body of research. Twenty-six studies were included with 538 PTSD participants, 254 non-trauma exposed control participants (NTC), and 276 trauma exposed control participants (TC). PTSD-relevant words impaired EST performance more among PTSD groups and TC groups compared to NTC groups. PTSD groups and TC groups did not differ. When examining within-subject effect sizes, PTSD-relevant words and generally threatening words impaired EST performance relative to neutral words among PTSD groups, and only PTSD-relevant words impaired performance among the TC groups. These patterns were not found among the NTC groups. Moderator analyses suggested that these effects were significantly greater in blocked designs compared to randomized designs, toward unmasked compared to masked stimuli, and among samples exposed to assaultive traumas compared to samples exposed to non-assaultive traumas. Theoretical and clinical implications are discussed.

Stress-induced activation of the brainstem Bcl-xL gene expression in rats treated with fluoxetine: correlations with serotonin metabolism and depressive-like behavior

Mechanisms underlying stress-induced depression and antidepressant drug action were shown to involve alterations in serotonergic (5-HT) neurotransmission and expression of genes coding for proteins associated with neurotrophic signaling pathways and cell-survival in the hippocampus and cortex. Expression of these genes in the brainstem containing 5-HT neurons may also be related to vulnerability or resilience to stress-related psychopathology. Here we investigated 5-HT markers and expression of genes for Brain-Derived Neurotrophic Factor (BDNF) and apoptotic proteins in the brainstem in relation to swim stress-induced behavioral despair. We found that anti-apoptotic Bcl-xL gene is sensitive to stress during the course of fluoxetine administration. Responsiveness of this gene to stress appeared concomitantly with an antidepressant-like effect of fluoxetine in the forced swim test. Bcl-xL transcript levels showed negative correlations with duration of immobility in the test and 5-HT turnover in the brainstem. In contrast, BDNF and pro-apoptotic protein Bax mRNA levels were unchanged by either fluoxetine or stress, suggesting specificity of Bcl-xL gene responses to these treatments. We also found that the levels of mRNAs for tryptophan hydroxylase-2 (TPH2) and 5-HT transporter (5-HTT) were significantly down-regulated following prolonged treatment with fluoxetine, but were not affected by stress. Unlike TPH2 and 5-HTT, 5-HT1A receptor mRNA levels were not altered by fluoxetine but significantly increased in response to swim stress. These data show that long-term fluoxetine treatment leads to changes in 5-HT and Bcl-xL responses to stress associated with antidepressant-like effects of the drug. This article is part of a Special Issue entitled 'Anxiety and Depression'.

Prenatal stress induces long term stress vulnerability, compromising stress response systems in the brain and impairing extinction of conditioned fear after adult stress

Stress is a risk factor for the development of affective disorders, including depression, post-traumatic stress disorder, and other anxiety disorders. However, not all individuals who experience either chronic stress or traumatic acute stress develop such disorders. Thus, other factors must confer a vulnerability to stress, and exposure to early-life stress may be one such factor. In this study we examined prenatal stress (PNS) as a potential vulnerability factor that may produce stable changes in central stress response systems and susceptibility to develop fear- and anxiety-like behaviors after adult stress exposure. Pregnant Sprague-Dawley rats were immobilized for 1 h daily during the last week of pregnancy. Controls were unstressed. The male offspring were then studied as adults. As adults, PNS or control rats were first tested for shock-probe defensive burying behavior, then half from each group were exposed to a combined chronic plus acute prolonged stress (CAPS) treatment, consisting of chronic intermittent cold stress (4 °C, 6 h/d, 14 days) followed on day 15 by a single session of sequential acute stressors (social defeat, immobilization, cold swim). After CAPS or control treatment, different groups were tested for open field exploration, social interaction, or cued fear conditioning and extinction. Rats were sacrificed at least 5 days after behavioral testing for measurement of tyrosine hydroxylase (TH) and glucocorticoid receptor (GR) expression in specific brain regions, and plasma adrenocorticotropic hormone (ACTH) and corticosterone. Shock-probe burying, open field exploration and social interaction were unaffected by any treatment. However, PNS elevated basal corticosterone, decreased GR protein levels in hippocampus and prefrontal cortex, and decreased TH mRNA expression in noradrenergic neurons in the dorsal pons. Further, rats exposed to PNS plus CAPS showed attenuated extinction of cue-conditioned fear. These results suggest that PNS induces vulnerability to subsequent adult stress, resulting in an enhanced fear-like behavioral profile, and dysregulation of brain noradrenergic and hypothalamic-pituitary-adrenal axis (HPA) activity.

Seeking a spotless mind: extinction, deconsolidation, and erasure of fear memory

Learning to contend with threats in the environment is essential to survival, but dysregulation of memories for traumatic events can lead to disabling psychopathology. Recent years have witnessed an impressive growth in our understanding of the neural systems and synaptic mechanisms underlying emotional memory formation. As a consequence, interest has emerged in developing strategies for suppressing, if not eliminating, fear memories. Here, I review recent work employing sophisticated behavioral, pharmacological, and molecular tools to target fear memories, placing these memories firmly behind the crosshairs of neurobiologically informed interventions.

Pretraumatic prolonged elevation of salivary MHPG predicts peritraumatic distress and symptoms of post-traumatic stress disorder

Post-traumatic stress disorder (PTSD) is associated with elevated catecholamines and increased sympathetic arousal. However, it is unknown whether this condition is a pre-existing vulnerability factor for PTSD or an acquired result of either trauma exposure or the development of PTSD symptoms. We sought to examine if salivary 3-methoxy-4-hydroxy-phenylglycol (MHPG) in response to a laboratory stressor prior to critical incident exposure predicts the development of PTSD symptoms and if early childhood trauma influences this relationship. In a prospective cohort study, 349 urban police officers were assessed during academy training (baseline) and 243 were reassessed 12 months after the start of active duty (follow-up). At baseline, participants observed a video consisting of police critical incidents. Salivary MHPG was measured before and immediately after the challenge, and after 20min recovery. At follow-up, peritraumatic distress and PTSD symptoms were assessed in relationship to the worst critical incident during the past year. Participants with childhood trauma showed a trend towards higher MHPG increase to the challenge. Higher MHPG levels after 20min recovery were associated with both higher levels of peritraumatic distress and PTSD symptoms at follow-up. In a path analysis, elevated MHPG levels predicted higher peritraumatic distress which in turn predicted higher levels of PTSD symptoms while the direct effect of elevated MHPG levels on PTSD symptoms was no longer significant. Prolonged elevation of salivary MHPG in response to a laboratory stressor marks a predisposition to experience higher levels of peritraumatic distress and subsequently more PTSD symptoms following critical incident exposure.

Perceived threat predicts the neural sequelae of combat stress

Exposure to severe stressors increases the risk for psychiatric disorders in vulnerable individuals, but can lead to positive outcomes for others. However, it remains unknown how severe stress affects neural functioning in humans and what factors mediate individual differences in the neural sequelae of stress. The amygdala is a key brain region involved in threat detection and fear regulation, and previous animal studies have suggested that stress sensitizes amygdala responsivity and reduces its regulation by the prefrontal cortex. In this study, we used a prospective design to investigate the consequences of severe stress in soldiers before and after deployment to a combat zone. We found that combat stress increased amygdala and insula reactivity to biologically salient stimuli across the group of combat-exposed individuals. In contrast, its influence on amygdala coupling with the insula and dorsal anterior cingulate cortex was dependent on perceived threat, rather than actual exposure, suggesting that threat appraisal affects interoceptive awareness and amygdala regulation. Our results demonstrate that combat stress has sustained consequences on neural responsivity, and suggest a key role for the appraisal of threat on an amygdala-centered neural network in the aftermath of severe stress.

Predicting impaired extinction of traumatic memory and elevated startle

BACKGROUND

Emotionally traumatic experiences can lead to debilitating anxiety disorders, such as phobias and Post-Traumatic Stress Disorder (PTSD). Exposure to such experiences, however, is not sufficient to induce pathology, as only up to one quarter of people exposed to such events develop PTSD. These statistics, combined with findings that smaller hippocampal size prior to the trauma is associated with higher risk of developing PTSD, suggest that there are pre-disposing factors for such pathology. Because prospective studies in humans are limited and costly, investigating such pre-dispositions, and thus advancing understanding of the genesis of such pathologies, requires the use of animal models where predispositions are identified before the emotional trauma. Most existing animal models are retrospective: they classify subjects as those with or without a PTSD-like phenotype long after experiencing a traumatic event. Attempts to create prospective animal models have been largely unsuccessful.

METHODOLOGY/PRINCIPAL FINDINGS

Here we report that individual predispositions to a PTSD-like phenotype, consisting of impaired rate and magnitude of extinction of an emotionally traumatic event coupled with long-lasting elevation of acoustic startle responses, can be revealed following exposure to a mild stressor, but before experiencing emotional trauma. We compare, in rats, the utility of several classification criteria and report that a combination of criteria based on acoustic startle responses and behavior in an anxiogenic environment is a reliable predictor of a PTSD-like phenotype.

CONCLUSIONS/SIGNIFICANCE

There are individual predispositions to developing impaired extinction and elevated acoustic startle that can be identified after exposure to a mildly stressful event, which by itself does not induce such a behavioral phenotype. The model presented here is a valuable tool for studying the etiology and pathophysiology of anxiety disorders and provides a platform for testing behavioral and pharmacological interventions that can reduce the probability of developing pathologic behaviors associated with such disorders.

Auditory aversive learning increases discrimination thresholds

Animal studies of discriminative fear conditioning traditionally use stimuli that are distant in physical features and thus easily distinguished perceptually. Independently, human studies have shown that training mostly improves discrimination thresholds. We found that aversive learning actually induced an increase in discrimination thresholds in humans and that subjective aversion during conditioning predicted the individual threshold change. This counterintuitive performance deterioration occurred when using odors or sounds as aversive reinforcers and was not a result of attentional distraction or decision bias. In contrast, positive reinforcement or mere exposure induced the typically reported decrease in thresholds. Our findings indicate that aversive outcomes induce wider stimulus generalization by modulating perceptual thresholds, suggesting the engagement of low-level mechanisms. We suggest that for risk- or loss-related stimuli, less specificity could be a benefit, as it invokes the same mechanisms that respond quickly and efficiently in the face of danger.

The effect of enriched environment on the outcome of traumatic brain injury; a behavioral, proteomics, and histological study

De novo hippocampal neurogenesis contributes to functional recovery following traumatic brain injury (TBI). Enriched environment (EEN) can improve the outcome of TBI by positively affecting neurogenesis. Blast induced traumatic brain injury (bTBI) characterized by memory impairment and increased anxiety levels, is a leading cause of chronic disability among soldiers. Using a rodent model of bTBI we asked: (a) whether long-term exposure to EEN after injury can ameliorate behavioral abnormalities and (b) what the effects of EEN are at the molecular and cellular levels and on de novo neurogenesis. We found that housing injured animals in EEN resulted in significantly improved spatial memory while animals in normal housing (NH) showed persistent memory impairment. VEGF and Tau protein but not Interleukin-6 (IL-6) levels were normalized in the dorsal hippocampus (DHC) of EEN rats while all three markers remained elevated in NH rats. Interestingly, after peaking at 6 weeks post-injury, anxiety returned to normal levels at 2 months independent of housing conditions. Housing animals in EEN had no significant effect on VEGF and Tau protein levels in the ventral hippocampus (VHC) and the amygdala (AD). We also found that EEN reduced IL-6 and IFNγ levels in the VHC; these markers remained elevated following NH. We observed an increase in GFAP and DCX immunoreactivities in the VHC of NH animals at 2 months post-injury. Conversely, injured animals housed in EEN showed no increase in GFAP or DCX immunoreactivity in their VHC. In summary, long-term exposure of injured animals to EEN appears to play a positive role in the restoration of memory functions but not on anxiety, which returned to normal levels after a significant period of time. Cellular and molecular changes in response to EEN appear to be a part of neurogenesis-independent as well as dependent recovery processes triggered by bTBI.

Transtorno de estresse pós-traumático: evolução dos critérios diagnósticos e prevalência

O transtorno de estresse pós-traumático (TEPT) se caracteriza por sintomas persistentes de revivência, evitação e entorpecimento, e excitabilidade aumentada, após a exposição a um evento traumático. Estudos epidemiológicos mostram que, entre os transtornos de ansiedade, o TEPT é o terceiro mais prevalente. Desde 1980, quando foi reconhecido como um diagnóstico válido, mudanças conceituais importantes ocorreram. A partir disso, o presente artigo apresenta uma revisão crítica da literatura sobre o desenvolvimento dos critérios diagnósticos do TEPT ao longo das edições do Manual diagnóstico e estatístico dos transtornos mentais (DSM), bem como informações sobre a prevalência do transtorno.

The basolateral amygdala regulates adaptation to stress via β-adrenergic receptor-mediated reductions in phosphorylated extracellular signal-regulated kinase

The reactivity of physiological systems and behavior to psychological stress is reduced with increasing familiarity with a repeated stressor. This reduced reactivity, termed habituation, is a crucial adaptation limiting negative health consequences of stress and can be disrupted in psychopathology. We hypothesized that the ability to habituate physiologically and behaviorally to previously experienced stressors depends on β-adrenergic receptor activation (β-AR) in the basolateral amygdala (BLA), a specific neural substrate important for the consolidation of multiple types of memories. We observed that administration of the β-AR antagonist propranolol into the BLA after each of four daily exposures to restraint stress prevented the normal development of neuroendocrine and behavioral habituation measured during the fifth restraint in adult male rats. In contrast, the β-AR agonist clenbuterol administered into the BLA after each restraint on days 1-4 enhanced neuroendocrine habituation at the lowest dose but attenuated behavioral habituation at high doses. We then explored intracellular signaling mechanisms in the BLA that might be a target of β-AR activation during stress. β-AR activation post restraint is necessary for the alteration in basal phosphorylated ERK (pERK) levels, as daily post-stress β-AR blockade on days 1-4 prevented repeated stress from leading to decreased pERK in the BLA on day 5. Finally, we examined the effect of blocking ERK phosphorylation in the BLA after each restraint on days 1-4 with the MEK (MAPK/ERK kinase) inhibitor U0126, and found that this was sufficient to both mimic neuroendocrine habituation in stress-naive animals and to enhance it in repeatedly stressed animals during restraint on day 5. Together, the results suggest that an individual's ability to habituate to repeated stress is regulated by activation of BLA β-AR, which may have these effects by transducing subsequent reductions in pERK. Individual variations in β-AR activation and intracellular signaling in the BLA may contribute significantly to adaptation to psychological stress and consequent resilience to stress-related psychopathology.

Post-traumatic stress disorder is associated with PACAP and the PAC1 receptor

Pituitary adenylate cyclase-activating polypeptide (PACAP) is known to broadly regulate the cellular stress response. In contrast, it is unclear if the PACAP/PAC1 receptor pathway has a role in human psychological stress responses, such as posttraumatic stress disorder (PTSD). In heavily traumatized subjects, we find a sex-specific association of PACAP blood levels with fear physiology, PTSD diagnosis and symptoms in females (N=64, replication N=74, p<0.005). Using a tag-SNP genetic approach (44 single nucleotide polymorphisms, SNPs) spanning the PACAP (ADCYAP1) and PAC1 (ADCYAP1R1) genes, we find a sex-specific association with PTSD. rs2267735, a SNP in a putative estrogen response element within ADCYAP1R1, predicts PTSD diagnosis and symptoms in females only (combined initial and replication samples: N=1237; p<2x10⁻5). This SNP also associates with fear discrimination and with ADCYAP1R1 mRNA expression. Methylation of ADCYAP1R1 is also associated with PTSD (p < 0.001). Complementing these human data, ADCYAP1R1 mRNA is induced with fear conditioning or estrogen replacement in rodent models. These data suggest that perturbations in the PACAP/PAC1 pathway are involved in abnormal stress responses underlying PTSD. These sex-specific effects may occur via estrogen regulation of ADCYAP1R1. PACAP levels and ADCYAP1R1 SNPs may serve as useful biomarkers to further our mechanistic understanding of PTSD.

Stress and traumatic brain injury: a behavioral, proteomics, and histological study

Psychological stress and traumatic brain injury (TBI) can both result in lasting neurobehavioral abnormalities. Post-traumatic stress disorder and blast induced TBI (bTBI) have become the most significant health issues in current military conflicts. Importantly, military bTBI virtually never occurs without stress. In this experiment, we assessed anxiety and spatial memory of rats at different time points after repeated exposure to stress alone or in combination with a single mild blast. At 2 months after injury or sham we analyzed the serum, prefrontal cortex (PFC), and hippocampus (HC) of all animals by proteomics and immunohistochemistry. Stressed sham animals showed an early increase in anxiety but no memory impairment at any measured time point. They had elevated levels of serum corticosterone (CORT) and hippocampal IL-6 but no other cellular or protein changes. Stressed injured animals had increased anxiety that returned to normal at 2 months and significant spatial memory impairment that lasted up to 2 months. They had elevated serum levels of CORT, CK-BB, NF-H, NSE, GFAP, and VEGF. Moreover, all of the measured protein markers were elevated in the HC and the PFC; rats had an increased number of TUNEL-positive cells in the HC and elevated GFAP and Iba1 immunoreactivity in the HC and the PFC. Our findings suggest that exposure to repeated stress alone causes a transient increase in anxiety and no significant memory impairment or cellular and molecular changes. In contrast, repeated stress and blast results in lasting behavioral, molecular, and cellular abnormalities characterized by memory impairment, neuronal and glial cell loss, inflammation, and gliosis. These findings may have implications in the development of diagnostic and therapeutic measures for conditions caused by stress or a combination of stress and bTBI.

Acupuncture for posttraumatic stress disorder: conceptual, clinical, and biological data support further research

Posttraumatic stress disorder (PTSD) is common, debilitating, and has highly heterogeneous clinical and biological features. With the exception of one published preliminary clinical trial, rationale in support of the efficacy of acupuncture, a modality of Chinese medicine (CM), for PTSD has not been well described. This is a focused review of conceptual and clinical features of PTSD shared by modern western medicine (MWM) and CM, and of biological mechanisms of acupuncture that parallel known PTSD pathology. MWM and CM both recognize individual developmental variables and interactions between external conditions and internal responses in the genesis of PTSD. There is one published and one unpublished clinical trial that preliminarily support the efficacy of acupuncture for PTSD. Although there have been no mechanistic studies of acupuncture in human PTSD, extant research shows that acupuncture has biological effects that are relevant to PTSD pathology. Conceptual, clinical, and biological data support possible efficacy of acupuncture for PTSD. However, further definitive research about simultaneous clinical and biological effects is needed to support the use of acupuncture for PTSD in health care systems.

Individual variation in the propensity to attribute incentive salience to an appetitive cue predicts the propensity to attribute motivational salience to an aversive cue

It has been proposed that animals that attribute high levels of incentive salience to reward-related cues may be especially vulnerable to addiction. Individual variation has also been observed in the motivational value attributed to aversive cues, which may confer vulnerability to anxiety disorders such as post-traumatic stress disorder (PTSD). There may be a core behavioral trait that contributes to individual variation in the motivational value assigned to predictive cues regardless of emotional valence. To test this hypothesis, we used a Pavlovian conditioned approach procedure to classify rats based on whether they learned to approach and interact with a cue predicting food reward (sign-trackers) or learned upon cue presentation to go to the location of impending food delivery (goal-trackers), and then examined Pavlovian fear conditioning in the same animals. It has recently been proposed that sign-trackers are more vulnerable to substance abuse because they attribute greater incentive motivational value to drug cues. Here we show that sign-trackers also have a tendency to be more fearful of discrete cues that predict footshock. In addition, we found that goal-trackers exhibited greater contextual fear when placed back into the original fear-conditioning context in the absence of temporally discrete cues. These results suggest that there may be a subset of individuals who tend to attribute high levels of motivational salience to predictive cues regardless of emotional valence, which may predispose them to a number of psychiatric comorbidities including PTSD and substance abuse. Other individuals use contexts to appropriately modify their reactions to such salient stimuli.

Block of glucocorticoid synthesis during re-activation inhibits extinction of an established fear memory

BACKGROUND

The pharmacology of traumatic memory extinction has not been fully characterized despite its potential as a therapeutic target for established, acquired anxiety disorders, including post-traumatic stress disorder (PTSD). Here we examine the role of endogenous glucocorticoids in traumatic memory extinction.

METHODS

Male C57BL/6J mice were injected with corticosterone (10 mg/kg, i.p.) or metyrapone (50 mg/kg, s.c.) during re-activation of a contextual fear memory, and compared to vehicle groups (N=10-12 per group). To ensure that metyrapone was blocking corticosterone synthesis, we measured corticosterone levels following re-activation of a fear memory in metyrapone- and vehicle-treated animals.

RESULTS

Corticosterone administration following extinction trials caused a long-lasting inhibition of the original fear memory trace. In contrast, blockade of corticosteroid synthesis with metyrapone prior to extinction trials enhanced retrieval and prevented extinction of context-dependent fear responses in mice. Further behavioral analysis suggested that the metyrapone enhancement of retrieval and prevention of extinction were not due to non-specific alterations in locomotor or anxiety-like behavior. In addition, the inhibition of extinction by metyrapone was rescued by exogenous administration of corticosterone following extinction trials. Finally, we confirmed that the rise in corticosterone during re-activation of a contextual fear memory was blocked by metyrapone.

CONCLUSIONS

We demonstrate that extinction of a classical contextual fear memory is dependent on endogenous glucocorticoid synthesis during re-activation of a fear memory. Our data suggest that decreased glucocorticoids during fear memory re-activation may contribute to the inability to extinguish a fear memory, thus contributing to one of the core symptoms of PTSD.

Post-traumatic stress disorder moderates the relation between documented childhood victimization and pain 30 years later

Cross-sectional designs and self-reports of maltreatment characterize nearly all the literature on childhood abuse or neglect and pain in adulthood, limiting potential for causal inference. The current study describes a prospective follow up of a large cohort of individuals with court-documented early childhood abuse or neglect (n=458) and a demographically matched control sample (n=349) into middle adulthood (mean age 41), nearly 30 years later, comparing the groups for risk of adult pain complaints. We examine whether Post-Traumatic Stress Disorder (PTSD) mediates or moderates risk of pain. Assessed prospectively across multiple pain measures, physically and sexually abused and neglected individuals generally showed a significant (p<.05) but notably small (η(2)=.01) increased risk of pain symptoms in middle adulthood. Although PTSD was associated with both childhood victimization (p<.01) and risk of middle adulthood pain (p<.001), it did not appear to mediate the relationship between victimization and pain. However, across all pain outcomes other than medically unexplained pain, PTSD robustly interacted with documented childhood victimization to predict adult pain risk: Individuals with both childhood abuse/neglect and PTSD were at significantly increased risk (p<.001, η(2) generally=.05-.06) of pain. After accounting for the combined effect of the two factors, neither childhood victimization nor PTSD alone predicted pain risk. Findings support a view that clinical pain assessments should focus on PTSD rather than make broad inquiries into past history of childhood abuse or neglect.