Hypersensitivity of the hypothalamic-pituitary-adrenal axis to naloxone in post-traumatic stress disorder

Proton Magnetic Resonance Spectroscopy in Post-Traumatic Stress Disorder-Updated Systematic Review and Meta-Analysis

A stressor-related disorder wherein traumatic experience precipitates protracted disruptions to mood and cognition, post-traumatic stress disorder (PTSD) is associated with wide-ranging abnormalities across the body. While various methods have investigated these deviations, only proton magnetic resonance spectroscopy (¹H MRS) enables noninvasive measurement of small-molecule metabolites in the living human. ¹H MRS has correspondingly been employed to test hypotheses about the composition and function of multiple brain regions putatively involved in PTSD. Here we systematically review methodological considerations and reported findings, both positive and negative, of the current ¹H-MRS literature in PTSD (N = 32 studies) to communicate the brain regional metabolite alterations heretofore observed, providing random-effects model meta-analyses for those most extensively studied. Our review suggests significant PTSD-associated decreases in N-acetyl aspartate in bilateral hippocampus and anterior cingulate cortex with less evident effect in other metabolites and regions. Model heterogeneities diverged widely by analysis (I² < 0.01% to 90.1%) and suggested regional dependence on quantification reference (creatine or otherwise). While observed variabilities in methods and reported findings suggest that ¹H-MRS explorations of PTSD could benefit from methodological standardization, informing this standardization by quantitative assessment of the existing literature is currently hampered by its small size and limited scope.

Twenty-Seven Tamoxifen-Inducible iCre-Driver Mouse Strains for Eye and Brain, Including Seventeen Carrying a New Inducible-First Constitutive-Ready Allele

To understand gene function, the cre/loxP conditional system is the most powerful available for temporal and spatial control of expression in mouse. However, the research community requires more cre recombinase expressing transgenic mouse strains (cre-drivers) that restrict expression to specific cell types. To address these problems, a high-throughput method for large-scale production that produces high-quality results is necessary. Further, endogenous promoters need to be chosen that drive cell type specific expression, or we need to further focus the expression by manipulating the promoter. Here we test the suitability of using knock-ins at the docking site 5′ of Hprt for rapid development of numerous cre-driver strains focused on expression in adulthood, using an improved cre tamoxifen inducible allele (icre/ERT2), and testing a novel inducible-first, constitutive-ready allele (icre/f3/ERT2/f3). In addition, we test two types of promoters either to capture an endogenous expression pattern (MaxiPromoters), or to restrict expression further using minimal promoter element(s) designed for expression in restricted cell types (MiniPromoters). We provide new cre-driver mouse strains with applicability for brain and eye research. In addition, we demonstrate the feasibility and applicability of using the locus 5′ of Hprt for the rapid generation of substantial numbers of cre-driver strains. We also provide a new inducible-first constitutive-ready allele to further speed cre-driver generation. Finally, all these strains are available to the research community through The Jackson Laboratory.

Recent advances in the neurobiology of posttraumatic stress disorder: A review of possible mechanisms underlying an effective pharmacotherapy

Recent progress in the field of neurobiology supported by clinical evidence gradually reveals the mystery of human brain functioning. So far, many psychiatric disorders have been described in great detail, although there are still plenty of cases that are misunderstood. These include posttraumatic stress disorder (PTSD), which is a unique disease that combines a wide range of neurobiological changes, which involve disturbances of the hypothalamic-pituitary-adrenal gland axis, hyperactivation of the amygdala complex, and attenuation of some hippocampal and cortical functions. Such multiplicity results in differential symptomatology, including elevated anxiety, nightmares, fear retrieval episodes that may trigger delusions and hallucinations, sleep disturbances, and many others that strongly interfere with the quality of the patient's life. Because of widespread neurological changes and the disease manifestation, the pharmacotherapy of PTSD remains unclear and requires a multidimensional approach and involvement of polypharmacotherapy. Hopefully, more and more neuroscientists and clinicians will study PTSD, which will provide us with new information that would possibly accelerate establishment of well-tolerated and effective pharmacotherapy. In this review, we have focused on neurobiological changes regarding PTSD, addressing the most disturbed brain structures and neurotransmissions, as well as discussing in detail the recently taken and novel therapeutic paths.

Adrenocortical responsiveness to infusions of physiological doses of ACTH is not altered in posttraumatic stress disorder

Early studies of posttraumatic stress disorder (PTSD) reported that abnormal function of the hypothalamic–pituitary–adrenocortical (HPA) system was associated with the disorder. However, subsequent studies attempting to identify a specific aspect of HPA dysfunction that characterizes PTSD have been marked by considerable inconsistency of results. A facet of HPA regulation that has been considered but not definitively investigated is the possibility that the responsiveness of the adrenal cortex to physiological concentrations of adrenocorticotropin (ACTH) is diminished in PTSD. Relationships between PTSD and the adrenal androgen dehydroepiandrosterone (DHEA) have also been postulated. In this study we investigated the magnitude and time course of changes in concentrations of plasma cortisol and DHEA in response to bolus infusions of physiological doses of ACTH _1–24 in PTSD patients and control subjects. We found no evidence for PTSD-related alterations in cortisol or DHEA secretion in response to stimulation by low doses of ACTH and conclude that adrenocortical responsiveness is normal in PTSD. Results from this and other studies suggest that the occurrence of defects in HPA function in PTSD may be specific responses to particular combinations of trauma type, genetic susceptibility, and individual history.

Assessment of HPA-axis function in posttraumatic stress disorder: pharmacological and non-pharmacological challenge tests, a review

Posttraumatic stress disorder (PTSD) is typically accompanied by acute and chronic alterations in the stress response. These alterations have mostly been described in individuals under baseline conditions, but several studies have also used a challenge model to further assess the role of the hypothalamic-pituitary-adrenal (HPA) axis in the stress response. This paper reviews common methodology and research findings on HPA function in PTSD, and discusses the pathophysiological mechanisms underlying these findings. We reviewed the literature and selected all English-language, human subject, data driven, pharmacological and non-pharmacological challenge studies pertaining to the HPA axis, and in vitro leukocyte glucocorticoid receptor studies in adult PTSD subjects. Studies using a non-pharmacological stress paradigm (cognitive stress, trauma reminders) to stimulate the HPA axis showed an exaggerated cortisol response in PTSD. The most widely used pharmacological challenge with consistent results was the low dose dexamethasone-suppression test (DST). These DST studies showed enhanced cortisol suppression in subjects with PTSD. Different hypotheses have been purported to explain the alterations in HPA axis functioning in PTSD. The results of the reviewed challenge tests, however, did not exclusively support one of the hypothesized mechanisms. Further research assessing hormones at all levels of the HPA axis at both baseline and at challenge conditions with a proper stratification of study population, will be necessary for a better understanding of stress-responsivity on the level of the HPA axis in PTSD.

Child maltreatment and HPA axis dysregulation: relationship to major depressive disorder and post traumatic stress disorder in females

A history of child maltreatment increases the vulnerability to the development of Major Depressive Disorder (MDD) and/or Posttraumatic Stress Disorder (PTSD), especially in females. Both MDD and PTSD are associated with a dysregulation of the Hypothalamic-Pituitary-Adrenal (HPA) axis. Dysregulation of the HPA axis may be an important etiological link between child maltreatment and subsequent psychiatric disorder, yet little is known about the relationship between exposure and outcome. The aim of this review is to explore the role of HPA axis dysregulation in the link between child maltreatment and MDD/PTSD among women. Studies of females with MDD frequently indicate a hyperactivity of the HPA axis, and contribute to our understanding of the underlying mechanisms involved in mood dysregulation. Evidence for HPA axis dysregulation in PTSD is less convincing and suggests that timing of the stressful experience as well as the type of the trauma may influence the outcome. The strongest evidence to date suggesting that the development of the HPA axis may be affected by early life stressful experiences comes from pre-clinical animal studies. Together these studies add to our understanding of the role of the HPA axis in psychiatric disorders in relation to stress. The literature on HPA axis function in both children and adults following child maltreatment further highlights the potential relevance of early stress to later onset of major psychiatric disorders. Such knowledge may also contribute to the development of early interventions targeted at primary prevention.

Neuroendocrine aspects of PTSD

This chapter discussed how neuroendocrine findings in posttraumatic stress disorder (PTSD) potentially inform hypothalamic-pituitary-adrenal (HPA) alterations in PTSD and highlight alterations relevant to the identification of targets for drug development. Most studies demonstrate alterations consistent with an enhanced negative feedback inhibition of cortisol on the pituitary, an overall hyperreactivity of other target tissues (adrenal gland, hypothalamus), or both in PTSD. However, findings of low cortisol and increased reactivity of the pituitary in PTSD are also consistent with reduced adrenal output. The observations in PTSD are part of a growing body of neuroendocrine data providing evidence of insufficient glucocorticoid signaling in stress-related neuropsychiatric disorders.

Hypothalamic-pituitary-adrenal alterations in PTSD: are they relevant to understanding cortisol alterations in cancer?

Recent studies of hypothalamic-pituitary-adrenal axis alterations in PTSD have demonstrated a specific type of hyperresponsivity of this stress hormonal system characterized by a greater negative feedback inhibition of cortisol, which may paradoxically serve to lower cortisol levels. The occurrence of cancer has been recently described by many investigators as an event that fulfills the DSM-IV criteria for a "traumatic event" that has been demonstrated in some cases to be linked with the subsequent development of PTSD. This review considers the extent to which neuroendocrine alterations observed in PTSD may be useful in understanding cortisol alterations involved in cancer.

Prevalence of post-traumatic stress disorder in fibromyalgia patients: overlapping syndromes or post-traumatic fibromyalgia syndrome?

OBJECTIVES

The primary aim of this study was to assess the frequency of post-traumatic stress disorder (PTSD) in patients with the fibromyalgia syndrome (FMS). The influence of gender on measures of PTSD in fibromyalgia (FM) patients also was examined.

METHODS

Seventy-seven consecutive patients (40 women and 37 men) who fulfilled the criteria for FM were asked to complete questionnaires measuring the prevalence and severity of symptoms of PTSD, anxiety, and depression. The subjects were divided in 2 groups based on the presence or absence of PTSD symptoms.

RESULTS

In this study, 57% of the FM sample had clinically significant levels of PTSD symptoms. The FM patients with PTSD reported significantly greater levels of avoidance, hyperarousal, reexperiencing, anxiety, and depression than did the patients without clinically significant levels of PTSD symptoms. The prevalence of PTSD among the FM patients in this study was significantly higher than in the general population. Women with FM and PTSD reported a greater number of past traumatic events than did their male counterparts.

CONCLUSIONS

The results represent the first comprehensive study applying structured clinical assessment of trauma exposure and PTSD to a group of FM patients. This study shows a significant overlap between FM and PTSD, according to the currently accepted diagnostic criteria for each.

Current status of cortisol findings in post-traumatic stress disorder

This article summarizes findings of hypothalamic-pituitary-adrenal axis alterations in post-traumatic stress disorder (PTSD) and evaluates likely reasons for the lack of agreement among published studies. Sources of variance caused by methodologic and interpretative differences are highlighted, but the disparate findings are explained as illustrating a more complex neuroendocrinology of PTSD than has previously been described.

The effects of naltrexone maintenance on the response to yohimbine in healthy volunteers

BACKGROUND

Preclinical research suggests that opiate antagonists may alter stress responsiveness. This study describes the effect of pretreatment with the opioid antagonist naltrexone on the response to a noradrenergic stressor, the alpha-2-receptor-antagonist, yohimbine, in healthy subjects. The current study was designed to compare the change in responses to yohimbine after 2 weeks of treatment with naltrexone to the response after at least 2 weeks of treatment with placebo.

METHODS

After a week of placebo naltrexone treatment, ten subjects were randomized into a double-blind cross-over to placebo or active naltrexone (50 mg p.o. daily) on weeks 2 to 4, and the converse condition for weeks 5 to 7. Subjects received challenges in a random, fixed sequence with placebo and active yohimbine (i.v., 0.2 mg/kg) on weeks 1, 4, and 7. The active-active combination generally had the strongest drug effects.

RESULTS

There were statistically significant (p < .05) interactions of naltrexone condition X yohimbine condition for subject ratings of "nervous," "not liking the drug effect," "talkative," and "urge to urinate," and a trend (p < .10) for cortisol levels.

CONCLUSIONS

The results suggest that clinically used naltrexone doses alter sensitivity to yohimbine.

The effect of naloxone on adrenocorticotropin and cortisol release: evidence for a reduced response in depression

BACKGROUND

Endogenous opioid peptides inhibit the hypothalamic-pituitary-adrenal (HPA) axis by influencing the release of hypothalamic corticotropin releasing factors. This study examines whether increased activity of the HPA axis in major depression is associated with reduced opioid tone.

METHODS

We measured the adrenocorticotropin (ACTH) and cortisol responses to an intravenous bolus of naloxone 0.125 microg/kg in 13 depressed outpatients and 13 healthy volunteers.

RESULTS

The mean cortisol response was significantly reduced (P<0.05), and the ACTH response was also non-significantly reduced in the depressed subjects.

CONCLUSIONS

These findings imply that the degree of inhibitory endogenous opioid tone is reduced in depression. Various mechanisms for the finding are discussed, including possible alteration in the function of alpha-adrenergic pathways.

CLINICAL IMPLICATIONS

Reduced endogenous opioid tone may explain why some depressed individuals self-medicate with opiates, and depression is associated with opiate withdrawal. Opioid pathways may have a role in the mechanism of action of antidepressant drugs, and may be of relevance in the development of novel antidepressants.

LIMITATIONS OF THE STUDY

The sample size was small, leading to a failure of the difference of the basal cortisol levels and also the delta ACTH between the groups to reach statistical significance.

Recognising post-traumatic stress in intensive care patients

'We may not be able to prevent stress or distress, but we can alter the intensity and duration of stress-related trauma by naming our demons, daring to struggle with them, and by creating healing communities.' (Chandler 1992, p 88) In order to create an environment in which the above process can take place it is incumbent upon nurses to assess patients in need and to institute appropriate intervention at an early stage. Critical care nurses have a particular responsibility to identify the seeds of post-traumatic stress and implement supportive and preventive strategies, primarily because of the numbers of traumatised victims passing through their care. Even so, there appears to be a dearth of critical care literature which addresses either assessment or intervention strategies relevant to this important aspect of practice. The purpose of this paper is to highlight aspects of assessment specific to post-traumatic stress through a critical analysis and explanation of its theoretical base. This will act as a precursor to providing direction on possible practice developments.

Endogenous opiates: 1993

This paper is the sixteenth installment of our annual review of research concerning the opiate system. It is restricted to papers published during 1993 that concern the behavioral effects of the endogenous opiate peptides, and does not include papers dealing only with their analgesic properties. The specific topics this year include stress; tolerance and dependence; eating; drinking; gastrointestinal, renal, and hepatic function; mental illness and mood; learning, memory, and reward; cardiovascular responses; respiration and thermoregulation; seizures and other neurological disorders; electrical-related activity; general activity and locomotion; development; immunological responses; and other behaviors.