GABA(A) receptor beta 3 subunit gene and psychiatric morbidity in a post-traumatic stress disorder population

Involvement of the GABAergic system in PTSD and its therapeutic significance

The neurobiological mechanism of post-traumatic stress disorder (PTSD) is poorly understood. The inhibition of GABA neurons, especially in the amygdala, is crucial for the precise regulation of the consolidation, expression, and extinction of fear conditioning. The GABAergic system is involved in the pathophysiological process of PTSD, with several studies demonstrating that the function of the GABAergic system decreases in PTSD patients. This paper reviews the preclinical and clinical studies, neuroimaging techniques, and pharmacological studies of the GABAergic system in PTSD and summarizes the role of the GABAergic system in PTSD. Understanding the role of the GABAergic system in PTSD and searching for new drug targets will be helpful in the treatment of PTSD.

Significance of GABAA Receptor for Cognitive Function and Hippocampal Pathology

The hippocampus is a primary area for contextual memory, known to process spatiotemporal information within a specific episode. Long-term strengthening of glutamatergic transmission is a mechanism of contextual learning in the dorsal cornu ammonis 1 (CA1) area of the hippocampus. CA1-specific immobilization or blockade of α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate (AMPA) receptor delivery can impair learning performance, indicating a causal relationship between learning and receptor delivery into the synapse. Moreover, contextual learning also strengthens GABA_A (gamma-aminobutyric acid) receptor-mediated inhibitory synapses onto CA1 neurons. Recently we revealed that strengthening of GABA_A receptor-mediated inhibitory synapses preceded excitatory synaptic plasticity after contextual learning, resulting in a reduced synaptic excitatory/inhibitory (E/I) input balance that returned to pretraining levels within 10 min. The faster plasticity at inhibitory synapses may allow encoding a contextual memory and prevent cognitive dysfunction in various hippocampal pathologies. In this review, we focus on the dynamic changes of GABA_A receptor mediated-synaptic currents after contextual learning and the intracellular mechanism underlying rapid inhibitory synaptic plasticity. In addition, we discuss that several pathologies, such as Alzheimer’s disease, autism spectrum disorders and epilepsy are characterized by alterations in GABA_A receptor trafficking, synaptic E/I imbalance and neuronal excitability.

The receptor hypothesis and the pathogenesis of depression: Genetic bases and biological correlates

Depression has become one of the most prevalent neuropsychiatric disorders characterized by anhedonia, anxiety, pessimism, or even suicidal thoughts. Receptor theory has been pointed out to explain the pathogenesis of depression, while it is still subject to debate. Additionally, gene abnormality accounts for nearly 40-50% of depression risk, which is a significant factor contributing to the onset of depression. Accordingly, studying on receptors and their gene abnormality are critical parts of the research on internal causes of depression. This review summarizes the pathogenesis of depression from six of the most related receptors and their associated genes, including N-methyl-D-aspartate receptor, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor, glucocorticoid receptor, 5-hydroxytryptamine receptor, GABA_A receptor α2, and dopamine receptor; and several "non-classic" receptors, such as metabotropic glutamate receptor, opioid receptor, and insulin receptor. These receptors have received considerable critical attention and are highly implicated in the onset of depression. We begin by providing the biological mechanisms of action of these receptors on the pathogenesis of depression. Then we review the historical and social context about these receptors. Finally, we discuss the limitations of the current state of knowledge and outline insights on future research directions, aiming to provide more novel targets and theoretical basis for the early prevention, accurate diagnosis and prompt treatment of depression.

The D2 dopamine receptor (DRD2) gene is associated with co-morbid depression, anxiety and social dysfunction in untreated veterans with post-traumatic stress disorder

Objective.

To identify clusters of patients with post-traumatic stress disorder (PTSD) according to symptom profile and to examine the association of the A1 allele of the D2 dopamine receptor (DRD2) gene with these clusters.

Method.

Fifty-seven untreated Caucasian Vietnam veterans with PTSD were administered the General Health Questionnaire-28 (GHQ) and the Mississippi Scale for combat-related PTSD. DRD2 allelic status was determined by PCR.

Results.

Subjects with the DRD2 Al allele compared to those without this allele had significantly higher scores on GHQ 2 (anxiety/insomnia), GHQ 3 (social dysfunction) and GHQ 4 (depression). Cluster analysis of the GHQ data identified two primary groups. A high psychopathology cluster (cluster 3), featured by high co-morbid levels of somatic concerns, anxiety/insomnia, social dysfunction and depression, and a low psychopathology cluster (cluster 1), manifested by the reverse pattern. Scores in each of the four GHQ groups were significantly higher in cluster 3 than cluster 1, as was Mississippi Scale PTSD score. DRD2 A1 allele veterans compared to those without this allele were significantly more likely to be found in the high than the low psychopathology cluster group.

Conclusions.

DRD2 variants are associated with severe co-morbid psychopathology in PTSD subjects.

Pre-deployment insomnia is associated with post-deployment post-traumatic stress disorder and suicidal ideation in US Army soldiers

Study Objectives

Insomnia is prevalent among military personnel and may increase risk of mental disorders and suicidal ideation. This study examined associations of pre-deployment insomnia with post-deployment post-traumatic stress disorder (PTSD) and suicidal ideation among US Army soldiers.

Methods

Soldiers from three Brigade Combat Teams completed surveys 1-2 months before deploying to Afghanistan in 2012 (T0), on return from deployment (T1), 3 months later (T2), and 9 months later (T3). Logistic regression was performed to estimate associations of pre-deployment (T0) insomnia with post-deployment (T2 or T3) PTSD and suicidal ideation among respondents who completed surveys at all waves (n = 4645). A hierarchy of models incorporated, increasing controls for pre-deployment risk factors and deployment experiences.

Results

Pre-deployment insomnia was associated with increased risk of post-deployment PTSD (adjusted odds ratio [AOR] = 3.14, 95% confidence interval [CI] = 2.58% to 3.82%, p < .0005) and suicidal ideation (AOR = 2.78, 95% CI = 2.07% to 3.74%, p < .0005) in models adjusting for sociodemographic characteristics and prior deployment history. Adjustment for other pre-deployment risk factors and deployment experiences attenuated these associations; however, insomnia remained significantly associated with post-deployment PTSD (AOR = 1.50, 95% CI = 1.19% to 1.89%, p = .001) and suicidal ideation (AOR = 1.43, 95% CI = 1.04% to 1.95%, p = .027). Subgroup models showed that pre-deployment insomnia was associated with incident PTSD (AOR = 1.55, 95% CI = 1.17% to 2.07%, p = .003) and suicidal ideation (AOR = 1.67, 95% CI = 1.16% to 2.40%, p = .006) among soldiers with no pre-deployment history of these problems.

Conclusions

Pre-deployment insomnia contributed to prediction of post-deployment PTSD and suicidal ideation in Army soldiers, suggesting that detection of insomnia could facilitate targeting of risk mitigation programs. Future studies should investigate whether treatment of insomnia helps prevent PTSD and suicidal ideation among deployed service members.

Understanding the Scientific Basis of Post-traumatic Stress Disorder (PTSD): Precision Behavioral Management Overrides Stigmatization

Post-traumatic stress disorder (PTSD) is a severe polygenic disorder triggered by environmental factors. Many polymorphic genes, particularly the genetic determinants of hypodopaminergia (low dopamine function), associate with a predisposition to PTSD as well as substance use disorder. Support from the National Institutes of Health for neuroimaging research and molecular, genetic applied technologies has improved understanding of brain reward circuitry functions that have inspired the development of new innovative approaches to their early diagnosis and treatment of some PTSD symptomatology and addiction. This review presents psychosocial and genetic evidence that vulnerability or resilience to PTSD can theoretically be impacted by dopamine regulation. From a neuroscience perspective, dopamine is widely accepted as a major neurotransmitter. Questions about how to modulate dopamine clinically in order to treat and prevent PTSD and other types of reward deficiency disorders remain. Identification of genetic variations associated with the relevant genotype-phenotype relationships can be characterized using the Genetic Addiction Risk Score (GARS®) and psychosocial tools. Development of an advanced genetic panel is under study and will be based on a new array of genes linked to PTSD. However, for now, the recommendation is that enlistees for military duty be given the opportunity to voluntarily pre-test for risk of PTSD with GARS, before exposure to environmental triggers or upon return from deployment as part of PTSD management. Dopamine homeostasis may be achieved via customization of neuronutrient supplementation "Precision Behavioral Management" (PBM™) based on GARS test values and other pro-dopamine regulation interventions like exercise, mindfulness, biosensor tracking, and meditation.

Sleep disturbance at pre-deployment is a significant predictor of post-deployment re-experiencing symptoms

Background: Insomnia is common in service members and associated with many mental and physical health problems. Recently, longitudinal data have been used to assess the impact of disturbed sleep on mental health outcomes. These studies have consistently shown relationships between sleep disturbance and development of mental illness. Objective: The present study examined the longitudinal relationship between sleep disturbance and PTSD symptomatology in a cohort of Marines and Navy Corpsmen deployed to Iraq and Afghanistan (n = 2,404) assessed prior to deployment, as well as at -3 and 6 months post-deployment. Additionally, we aimed to investigate the extent to which these relationships are moderated by combat-stress severity, and to what extent these findings are replicated in a second, separate cohort of Marines and Navy corpsmen (n = 938) assessed with identical measures prior to deployment and within 3 months of return. Method: The present study employed latent variable path models to examine the relationships between pre-deployment sleep disturbance and post-deployment re-experiencing symptoms. Initial cross-lagged path models were conducted on discovery and replication samples to validate the hypothesized predictive relationships. Follow up moderation path models were then conducted to include the effect of combat-stress severity on these relationships. Results: Initial cross-lagged models supported a significant relationship between pre-deployment sleep disturbance and future re-experiencing PTSD symptoms at all time points. Initial moderation models showed a small moderator effect of combat-stress severity, though the main predictive relationship between pre-deployment sleep disturbance and PTSD symptoms remained significant. The moderator effect was not significant in the replication sample. Conclusions: The results of this study support pre-deployment sleep disturbance as a risk factor for development of post-deployment PTSD symptoms. Interventions aimed at normalizing sleep may be important in preventive measures for PTSD.

Pharmacogenetics and Pharmacotherapy of Military Personnel Suffering from Post-traumatic Stress Disorder

Background:

Posttraumatic stress disorder (PTSD) is a severe problem among soldiers with combating experience difficult to treat. The pathogenesis is still not fully understood at the psychological level. Therefore, genetic research became a focus of interest. The identification of single nucleotide polymorphisms (SNPs) may help to predict, which persons are at high risk to develop PTSD as a starting point to develop novel targeted drugs for treatment.

Methods:

We conducted a systematic review on SNPs in genes related to PTSD pathology and development of targeted pharmacological treatment options based on PubMed database searches. We focused on clinical trials with military personnel.

Results:

SNPs in 22 human genes have been linked to PTSD. These genes encode proteins acting as neurotransmitters and receptors, downstream signal transducers and metabolizing enzymes. Pharmacological inhibitors may serve as drug candidates for PTSD treatment, e.g. β2 adrenoreceptor antagonists, dopamine antagonists, partial dopamine D2 receptor agonists, dopamine β hydroxylase inhibitors, fatty acid amid hydrolase antagonists, glucocorticoid receptor agonists, tropomyosin receptor kinase B agonists, selective serotonin reuptake inhibitors, catechol-O-methyltransferase inhibitors, gamma-amino butyric acid receptor agonists, glutamate receptor inhibitors, monoaminoxidase B inhibitors, N-methyl-d-aspartate receptor antagonists.

Conclusion:

The combination of genetic and pharmacological research may lead to novel target-based drug developments with improved specificity and efficacy to treat PTSD. Specific SNPs may be identified as reliable biomarkers to assess individual disease risk. Focusing on soldiers suffering from PTSD will not only help to improve treatment options for this specific group, but for all PTSD patients and the general population.

Neurobiological Mechanisms of Stress Resilience and Implications for the Aged Population

BACKGROUND

Stress is a common reaction to an environmental adversity, but a dysregulation of the stress response can lead to psychiatric illnesses such as major depressive disorder (MDD), post-traumatic stress disorder (PTSD), and anxiety disorders. Yet, not all individuals exposed to stress will develop psychiatric disorders; those with enhanced stress resilience mechanisms have the ability to adapt successfully to stress without developing persistent psychopathology. Notably, the potential to enhance stress resilience in at-risk populations may prevent the onset of stress-induced psychiatric disorders. This novel idea has prompted a number of studies probing the mechanisms of stress resilience and how it can be manipulated.

METHODS

Here, we review the neurobiological factors underlying stress resilience, with particular focus on the serotoninergic (5-HT), glutamatergic, and γ-Aminobutyric acid (GABA) systems, as well as the hypothalamic-pituitary axis (HPA) in rodents and in humans. Finally, we discuss stress resiliency in the context of aging, as the likelihood of mood disorders increases in older adults.

RESULTS

Interestingly, increased resiliency has been shown to slow aging and improved overall health and quality of life. Research in the neurobiology of stress resilience, particularly throughout the aging process, is a nascent, yet, burgeoning field.

CONCLUSION

Overall, we consider the possible methods that may be used to induce resilient phenotypes, prophylactically in at-risk populations, such as in military personnel or in older MDD patients. Research in the mechanisms of stress resilience may not only elucidate novel targets for antidepressant treatments, but also provide novel insight about how to prevent these debilitating disorders from developing.

Is plasma GABA level a biomarker of Post-Traumatic Stress Disorder (PTSD) severity? A preliminary study

OBJECTIVES

An increased reactivity to the environment is observed in Post-Traumatic Stress Disorder (PTSD). It would be related to impairment of the Gamma Amino Butyric Acid (GABA) neurotransmission. The study aimed to evaluate plasma GABA concentration as a candidate for PTSD severity biomarker.

METHODS

This hypothesis was studied in 17 PTSD patients and 17 healthy Controls using classic and emotional Stroop paradigms. Plasma GABA concentrations were assessed before and after both Stroop tests to evaluate GABA basal tone and GABA reactivity (change in GABAp), respectively.

RESULTS

During baseline, PTSD had lower plasma GABA concentrations than the Controls. After the Stroop conflicts GABA reactivity was also lower in PTSD than in the Controls. The GABA baseline tone was negatively correlated with the severity of the PTSD symptoms. This relation was only marginally observed for GABA reactivity. The results produced a trend due to the small size of the sample compared to the number of statistical results given.

CONCLUSION

Altogether, the reduced GABA concentration observed in PTSD could be considered as a possible biomarker for PTSD severity.

Multimodal and Site-Specific Plasticity of Amygdala Parvalbumin Interneurons after Fear Learning

Stimulus processing in fear conditioning is constrained by parvalbumin interneurons (PV-INs) through inhibition of principal excitatory neurons. However, the contributions of PV-IN microcircuits to input gating and long-term plasticity in the fear system remain unknown. Here we interrogate synaptic connections between afferent pathways, PV-INs, and principal excitatory neurons in the basolateral amygdala. We find that subnuclei of this region are populated two functionally distinct PV-IN networks. PV-INs in the lateral (LA), but not the basal (BA), amygdala possess complex dendritic arborizations, receive potent excitatory drive, and mediate feedforward inhibition onto principal neurons. After fear conditioning, PV-INs exhibit nucleus- and target-selective plasticity, resulting in persistent reduction of their excitatory input and inhibitory output in LA but not BA. These data reveal previously overlooked specializations of amygdala PV-INs and indicate specific circuit mechanisms for inhibitory plasticity during the encoding of associative fear memories.

A Shared Molecular and Genetic Basis for Food and Drug Addiction: Overcoming Hypodopaminergic Trait/State by Incorporating Dopamine Agonistic Therapy in Psychiatry

This article focuses on the shared molecular and neurogenetics of food and drug addiction tied to the understanding of reward deficiency syndrome. Reward deficiency syndrome describes a hypodopaminergic trait/state that provides a rationale for commonality in approaches for treating long-term reduced dopamine function across the reward brain regions. The identification of the role of DNA polymorphic associations with reward circuitry has resulted in new understanding of all addictive behaviors.

Differential modulation of synaptic plasticity and local circuit activity in the dentate gyrus and CA1 regions of the rat hippocampus by corticosterone

Depending on its severity, timing and context, stress has been shown to have a differential regional effect on hippocampal synaptic plasticity. While the focus of attention in most recent studies is on excitatory synapses and generation, modifications of inhibitory synapses and local interneurons cannot be ignored. We have now examined the effects of corticosterone (CORT) on extrinsic afferent and local circuit plasticity of the perforant path on the dentate gyrus (DG) and the ventral hippocampal commissure on CA1. Local circuit activity was measured by responses to paired-pulse stimulation. Control rats expressed afferent long-term potentiation (LTP) and local circuit plasticity in both the DG and CA1. Administration of a high dosage of CORT-reduced paired-pulse inhibition and increased facilitation in DG but not in CA1, whereas administration of a moderate CORT dosage had no effect. Moderate CORT doses caused enhancement of LTP in the DG but not in CA1, while high CORT doses converted LTP to long-term depression in the CA1 but had no effect in the DG. CORT blocked theta burst stimulation-induced local circuit plasticity otherwise found in control DG. These findings suggest that elevation of the level of CORT results in a regionally differentiated physiological response. In addition, the results indicate that CORT affects aspects of local circuit activity and plasticity in the DG but less so in the CA1. It is possible that these differentiated alterations underlie some of the behavioral consequences and memory processes under stressful conditions.

GAD65 haplodeficiency conveys resilience in animal models of stress-induced psychopathology

GABAergic mechanisms are critically involved in the control of fear and anxiety, but their role in the development of stress-induced psychopathologies, including post-traumatic stress disorder (PTSD) and mood disorders is not sufficiently understood. We studied these functions in two established mouse models of risk factors for stress-induced psychopathologies employing variable juvenile stress and/or social isolation. A battery of emotional tests in adulthood revealed the induction of contextually generalized fear, anxiety, hyperarousal and depression-like symptoms in these paradigms. These reflect the multitude and complexity of stress effects in human PTSD patients. With factor analysis we were able to identify parameters that reflect these different behavioral domains in stressed animals and thus provide a basis for an integrated scoring of affectedness more closely resembling the clinical situation than isolated parameters. To test the applicability of these models to genetic approaches we further tested the role of GABA using heterozygous mice with targeted mutation of the GABA synthesizing enzyme GAD65 [GAD65(+/−) mice], which show a delayed postnatal increase in tissue GABA content in limbic and cortical brain areas. Unexpectedly, GAD65(+/−) mice did not show changes in exploratory activity regardless of the stressor type and were after the variable juvenile stress procedure protected from the development of contextual generalization in an auditory fear conditioning experiment. Our data demonstrate the complex nature of behavioral alterations in rodent models of stress-related psychopathologies and suggest that GAD65 haplodeficiency, likely through its effect on the postnatal maturation of GABAergic transmission, conveys resilience to some of these stress-induced effects.

Baclofen add-on to citalopram in treatment of posttraumatic stress disorder

OBJECTIVE

Posttraumatic stress disorder (PTSD) is a chronic disabling illness, resulting from exposure to extreme traumatic event. Although different pharmacologic agents are suggested for treatment of PTSD, none have been completely effective in eliminating symptoms. The purpose of this study was to assess the use of baclofen as an add-on to citalopram in treatment of PTSD.

METHODS

In this double-blind clinical trial, 40 Iranian combat veterans with PTSD were randomly assigned to 2 groups. The first group received a combination treatment of 20 to 60 mg/d citalopram and 40 mg/d baclofen, and the second group received 20 to 60 mg/d citalopram plus placebo. Symptom severity was assessed by Clinician-Administered PTSD Scale at the beginning of the study and after 2, 4, 6, and 8 weeks. Global Assessment of Functioning and Hamilton Rating Scale for Anxiety and Depression were also used at the same periods. Data were analyzed with independent t test and paired t test using SPSS software version 13 (IBM, Armonk, NY).

RESULTS

Twenty-three male patients (baclofen group, 13 patients; placebo group, 10 patients) completed the study. Dropout from the treatment was not caused by adverse effects of the new medications in any of the subjects. Baclofen group showed significantly larger improvement in Clinician-Administered PTSD Scale total (P = 0.040), hyperarousal (P = 0.020), and avoidance (0.020) scores, Global Assessment of Functioning score (0.001), depression (P = 0.000), and anxiety (P = 0.000) after 8 weeks of treatment. No intergroup difference was found in improvement of reexperience symptoms (P = 0.740).

CONCLUSIONS

Baclofen showed to be an effective add-on to selective serotonin reuptake inhibitors in treatment of PTSD for better symptom recovery and functional improvement.

The role of the serotonergic and GABA system in translational approaches in drug discovery for anxiety disorders

There is ample evidence that genetic factors play an important role in anxiety disorders. In support, human genome-wide association studies have implicated several novel candidate genes. However, illumination of such genetic factors involved in anxiety disorders has not resulted in novel drugs over the past decades. A complicating factor is the heterogeneous classification of anxiety disorders in the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-TR) and diverging operationalization of anxiety used in preclinical and clinical studies. Currently, there is an increasing focus on the gene × environment (G × E) interaction in anxiety as genes do not operate in isolation and environmental factors have been found to significantly contribute to the development of anxiety disorders in at-risk individuals. Nevertheless, extensive research on G × E mechanisms in anxiety has not resulted in major breakthroughs in drug discovery. Modification of individual genes in rodent models has enabled the specific study of anxiety in preclinical studies. In this context, two extensively studied neurotransmitters involved in anxiety are the gamma-aminobutyric acid (GABA) and 5-HT (5-hydroxytryptamine) system. In this review, we illustrate the complex interplay between genes and environment in anxiety processes by reviewing preclinical and clinical studies on the serotonin transporter (5-HTT), 5-HT1A receptor, 5-HT2 receptor, and GABAA receptor. Even though targets from the serotonin and GABA system have yielded drugs with known anxiolytic efficacy, the relation between the genetic background of these targets and anxiety symptoms and development of anxiety disorders is largely unknown. The aim of this review is to show the vast complexity of genetic and environmental factors in anxiety disorders. In light of the difficulty with which common genetic variants are identified in anxiety disorders, animal models with translational validity may aid in elucidating the neurobiological background of these genes and their possible role in anxiety. We argue that, in addition to human genetic studies, translational models are essential to map anxiety-related genes and to enhance our understanding of anxiety disorders in order to develop potentially novel treatment strategies.

Dopamine Genetics and Function in Food and Substance Abuse

Having entered the genomics era with confidence in the future of medicine, including psychiatry, identifying the role of DNA and polymorphic associations with brain reward circuitry has led to a new understanding of all addictive behaviors. It is noteworthy that this strategy may provide treatment for the millions who are the victims of "Reward Deficiency Syndrome" (RDS) a genetic disorder of brain reward circuitry. This article will focus on drugs and food being mutuality addictive, and the role of dopamine genetics and function in addictions, including the interaction of the dopamine transporter, and sodium food. We will briefly review our concept that concerns the genetic antecedents of multiple-addictions (RDS). Studies have also shown that evaluating a panel of established reward genes and polymorphisms enables the stratification of genetic risk to RDS. The panel is called the "Genetic Addiction Risk Score (GARS)", and is a tool for the diagnosis of a genetic predisposition for RDS. The use of this test, as pointed out by others, would benefit the medical community by identifying at risk individuals at a very early age. We encourage, in depth work in both animal and human models of addiction. We encourage further exploration of the neurogenetic correlates of the commonalities between food and drug addiction and endorse forward thinking hypotheses like "The Salted Food Addiction Hypothesis".

Promoter variants determine γ-aminobutyric acid homeostasis-related gene transcription in human epileptic hippocampi

The functional consequences of single nucleotide polymorphisms associated with episodic brain disorders such as epilepsy and depression are unclear. Allelic associations with generalized epilepsies have been reported for single nucleotide polymorphisms rs1883415 (ALDH5A1; succinic semialdehyde dehydrogenase) and rs4906902 (GABRB3; GABAA β3), both of which are present in the 5' regulatory region of genes involved in γ-aminobutyric acid (GABA) homeostasis. To address their allelic association with episodic brain disorders and allele-specific impact on the transcriptional regulation of these genes in human brain tissue, DNA and messenger RNA (mRNA) isolated from hippocampi were obtained at epilepsy surgery of 146 pharmacoresistant mesial temporal lobe epilepsy (mTLE) patients and from 651 healthy controls. We found that the C allele of rs1883415 is accumulated to a greater extentin mTLE versus controls. By real-time quantitative reverse transcription-polymerase chain reaction analyses, individuals homozygous for the C allele showed higher ALDH5A1 mRNA expression. The rs4906902 G allele of the GABRB3 gene was overrepresented in mTLE patients with depression; individuals homozygous for the G allele showed reduced GABRB3 mRNA expression. Bioinformatic analyses suggest that rs1883415 and rs4906902 alter the DNA binding affinity of the transcription factors Egr-3 in ALDH5A1 and MEF-2 in GABRB3 promoters, respectively. Using in vitro luciferase transfection assays, we observed that, in both cases, the transcription factors regulate gene expression depending on the allelic variant in the same direction as in the human hippocampi. Our data suggest that distinct promoter variants may sensitize individuals for differential, potentially stimulus-induced alterations of GABA homeostasis-relevant gene expression. This might contribute to the episodic onset of symptoms and point to new targets for pharmacotherapies.

Up-regulation of neurosteroid biosynthesis as a pharmacological strategy to improve behavioural deficits in a putative mouse model of post-traumatic stress disorder

Benzodiazepines remain the most frequently used psychotropic drugs for the treatment of anxiety spectrum disorders; however, their use is associated with the development of tolerance and dependence. Another major hindrance is represented by their lack of efficacy in many patients, including patients with post-traumatic stress disorder (PTSD). For these nonresponders, the use of selective serotonin reuptake inhibitors (SSRIs) has been the therapy of choice. In the past decade, clinical studies have suggested that the pharmacological action of SSRIs may include the ability of these drugs to normalise decreased brain levels of neurosteroids in patients with depression and PTSD; in particular, the progesterone derivative allopregnanolone, which potently, positively and allosterically modulates the action of GABA at GABA(A) receptors. Preclinical studies using the socially-isolated mouse as an animal model of PTSD have demonstrated that fluoxetine and congeners ameliorate anxiety-like behaviour, fear responses and aggressive behaviour expressed by such mice by increasing corticolimbic levels of allopregnanolone. This is a novel and more selective mechanism than serotonin reuptake inhibition, which, for half a century, has been considered to be the main molecular mechanism for the therapeutic action of SSRIs. Importantly, this finding may shed light on the high rates of SSRI resistance among patients with PTSD and depression, comprising disorders in which there appears to be a block in allopregnanolone synthesis. There are several different mechanisms by which such a block may occur, and SSRIs may only be corrective under some conditions. Thus, the up-regulation of allopregnanolone biosynthesis in corticolimbic neurones may offer a novel nontraditional pharmacological target for a new generation of potent nonsedating, anxiolytic medications for the treatment of anxiety, depression, and PTSD: selective brain steroidogenic stimulants.

Diagnosis and Healing In Veterans Suspected of Suffering from Post-Traumatic Stress Disorder (PTSD) Using Reward Gene Testing and Reward Circuitry Natural Dopaminergic Activation

There is a need for understanding and treating post-traumatic stress disorder (PTSD), in soldiers returning to the United States of America after combat. Likewise, it would be beneficial to finding a way to reduce violence committed by soldiers, here and abroad, who are suspected of having post-traumatic stress disorder (PTSD). We hypothesize that even before combat, soldiers with a childhood background of violence (or with a familial susceptibility risk) would benefit from being genotyped for high-risk alleles. Such a process could help to identify candidates who would be less suited for combat than those without high-risk alleles. Of secondary importance is finding safe methods to treat individuals already exposed to combat and known to have PTSD. Since hypodopaminergic function in the brain's reward circuitry due to gene polymorphisms is known to increase substance use disorder in individuals with PTSD, it might be parsimonious to administer dopaminergic agonists to affect gene expression (mRNA) to overcome this deficiency.

Neuro-psychopharmacogenetics and Neurological Antecedents of Posttraumatic Stress Disorder: Unlocking the Mysteries of Resilience and Vulnerability

BACKGROUND AND HYPOTHESIS

Although the biological underpinnings of immediate and protracted trauma-related responses are extremely complex, 40 years of research on humans and other mammals have demonstrated that trauma (particularly trauma early in the life cycle) has long-term effects on neurochemical responses to stressful events. These effects include the magnitude of the catecholamine response and the duration and extent of the cortisol response. In addition, a number of other biological systems are involved, including mesolimbic brain structures and various neurotransmitters. An understanding of the many genetic and environmental interactions contributing to stress-related responses will provide a diagnostic and treatment map, which will illuminate the vulnerability and resilience of individuals to Posttraumatic Stress Disorder (PTSD).

PROPOSAL AND CONCLUSIONS

We propose that successful treatment of PTSD will involve preliminary genetic testing for specific polymorphisms. Early detection is especially important, because early treatment can improve outcome. When genetic testing reveals deficiencies, vulnerable individuals can be recommended for treatment with "body friendly" pharmacologic substances and/or nutrients. Results of our research suggest the following genes should be tested: serotoninergic, dopaminergic (DRD2, DAT, DBH), glucocorticoid, GABAergic (GABRB), apolipoprotein systems (APOE2), brain-derived neurotrophic factor, Monamine B, CNR1, Myo6, CRF-1 and CRF-2 receptors, and neuropeptide Y (NPY). Treatment in part should be developed that would up-regulate the expression of these genes to bring about a feeling of well being as well as a reduction in the frequency and intensity of the symptoms of PTSD.

Psychogenetics of post-traumatic stress disorder: a short review

Post-traumatic stress disorder is a commonly overlooked psychiatric disorder due to the heterogeneity of symptoms that may simulate many other psychiatric disorders. Such heterogeneity of manifestations may be explained by the multifaceted nature of the different neurotransmitters, endocrinologic axis, and their genetic basis, that are implicated in the etiology. Although this disorder has been studied from many different perspectives, its etiology is still enigmatic. This minireview demonstrates, in brief, that different susceptibility genes are associated with post traumatic stress disorder.

How the neurocircuitry and genetics of fear inhibition may inform our understanding of PTSD

Exposure to traumatic events that produce extreme fear and horror is all too common in both military and civilian populations, but not all individuals develop posttraumatic stress disorder (PTSD) as a result of the exposure. What mediates risk and resilience in the development of PTSD and other stress-related psychopathology is of paramount importance to our further understanding of trauma-related psychopathology as well as the development of new treatment approaches. Biological factors, such as genotype and neurobiology, interact with environmental factors, such as childhood background and trauma load, to affect vulnerability and resilience in the aftermath of trauma exposure. One of the core symptoms of PTSD is the inability to control fear, which has led some investigators and clinicians to conceptualize PTSD as a disorder of fear or, more importantly, its inhibition. This review focuses on translational methods that have been used to examine fear conditioning and inhibition of fear in PTSD and summarizes genetic and neurobiological factors related to fear inhibition. The authors also discuss different pharmacological approaches that enhance fear inhibition and may improve treatment outcomes for patients with PTSD.

Enhanced expression of the neuronal K+/Cl- cotransporter, KCC2, in spontaneously depressed Flinders Sensitive Line rats

We used Flinder Sensitive Line (FSL) rats, a genetic model of unipolar depression, to examine whether changes in central GABAergic transmission are associated with a depressed phenotype. FSL rats showed an increased behavioral response to low doses of diazepam, as compared to either Sprague Dawley (SD) or Flinder Resistant Line (FRL) rats used as controls. Diazepam at a dose of 0.3 mg/kg, i.p., induced a robust impairment of motor coordination in FSL rats, but was virtually inactive in SD or FRL rats. The increased responsiveness of FSL rats was not due to changes in the brain levels of diazepam or its active metabolites, or to increases in the number or affinity of benzodiazepine recognition sites, as shown by the analysis of [(3)H]-flunitrazepam binding in the hippocampus, cerebral cortex or cerebellum. We therefore examined whether FSL rats differed from control rats for the expression levels of the K(+)/Cl(-) cotransporter, KCC2, which transports Cl(-) ions out of neurons, thus creating the concentration gradient that allows Cl(-) influx through the anion channel associated with GABA(A) receptors. Combined immunoblot and immunohistochemical data showed a widespread increase in KCC2 expression in FSL rats, as compared with control rats. The increase was more prominent in the cerebellum, where KCC2 was largely expressed in the granular layer. These data raise the interesting possibility that a spontaneous depressive state in animals is associated with an amplified GABAergic transmission in the CNS resulting from an enhanced expression of KCC2.

The hyperarousal model of insomnia: a review of the concept and its evidence

Primary insomnia is defined as difficulties in falling asleep, maintaining sleep or non-restorative sleep accompanied by significantly impaired daytime functioning in the absence of a specific physical, mental or substance-related cause. The current review provides substantial support for the concept that hyperarousal processes from the molecular to the higher system level play a key role in the pathophysiology of primary insomnia. Autonomous, neuroendocrine, neuroimmunological, electrophysiological and neuroimaging studies demonstrate increased levels of arousal in primary insomnia during both night and daytime. In the light of neurobiological theories of sleep-wake regulation, primary insomnia may be conceptualized as a final common pathway resulting from the interplay between a genetic vulnerability for an imbalance between arousing and sleep-inducing brain activity, psychosocial/medical stressors and perpetuating mechanisms including dysfunctional sleep-related behavior, learned sleep preventing associations and other cognitive factors like tendency to worry/ruminate.

The GABA transporter 1 (SLC6A1): a novel candidate gene for anxiety disorders

Recent evidence suggests that the GABA transporter 1 (GAT-1; SLC6A1) plays a role in the pathophysiology and treatment of anxiety disorders. In order to understand the impact of genetic variation within SLC6A1 on pathological anxiety, we performed a case–control association study with anxiety disorder patients with and without syndromal panic attacks. Using the method of sequential addition of cases, we found that polymorphisms in the 5′ flanking region of SLC6A1 are highly associated with anxiety disorders when considering the severity of syndromal panic attacks as phenotype covariate. Analysing the effect size of the association, we observed a constant increase in the odds ratio for disease susceptibility with an increase in panic severity (OR ~ 2.5 in severely affected patients). Nominally significant association effects were observed considering the entire patient sample. These data indicate a high load of genetic variance within SLC6A1 on pathological anxiety and highlight GAT-1 as a promising target for treatment of anxiety disorders with panic symptoms.

Exposure to forced swim stress alters local circuit activity and plasticity in the dentate gyrus of the hippocampus

Studies have shown that, depending on its severity and context, stress can affect neural plasticity. Most related studies focused on synaptic plasticity and long-term potentiation (LTP) of principle cells. However, evidence suggests that following high-frequency stimulation, which induces LTP in principal cells, modifications also take place at the level of complex interactions with interneurons within the dentate gyrus, that is, at the local circuit level. So far, the possible effects of stress on local circuit activity and plasticity were not studied. Therefore, we set out to examine the possible alterations in local circuit activity and plasticity following exposure to stress. Local circuit activity and plasticity were measured by using frequency dependant inhibition (FDI) and commissural modulation protocols following exposure to a 15 minute-forced swim trial. Exposure to stress did not alter FDI. The application of theta-burst stimulation (TBS) reduced FDI in both control and stressed rats, but this type of plasticity was greater in stressed rats. Commissural-induced inhibition was significantly higher in stressed rats both before and after applying theta-burst stimulation. These findings indicate that the exposure to acute stress affects aspects of local circuit activity and plasticity in the dentate gyrus. It is possible that these alterations underlie some of the behavioral consequences of the stress experience.

Gene-environment interaction in posttraumatic stress disorder: review, strategy and new directions for future research

The purpose of this article is to encourage research investigating the role of measured gene-environment interaction (G x E) in the etiology of posttraumatic stress disorder (PTSD). PTSD is uniquely suited to the study of G x E as the diagnosis requires exposure to a potentially-traumatic life event. PTSD is also moderately heritable; however, the role of genetic factors in PTSD etiology has been largely neglected both by trauma researchers and psychiatric geneticists. First, we summarize evidence for genetic influences on PTSD from family, twin, and molecular genetic studies. Second, we discuss the key challenges in G x E studies of PTSD and offer practical strategies for addressing these challenges and for discovering replicable G x E for PTSD. Finally, we propose some promising new directions for PTSD G x E research. We suggest that G x E research in PTSD is essential to understanding vulnerability and resilience following exposure to a traumatic event.

Role of GABA in anxiety and depression

This review assesses the parallel data on the role of gamma-aminobutyric acid (GABA) in depression and anxiety. We review historical and new data from both animal and human experimentation which have helped define the key role for this transmitter in both these mental pathologies. By exploring the overlap in these conditions in terms of GABAergic neurochemistry, neurogenetics, brain circuitry, and pharmacology, we develop a theory that the two conditions are intrinsically interrelated. The role of GABAergic agents in demonstrating this interrelationship and in pointing the way to future research is discussed.

Candidate genes for panic disorder: insight from human and mouse genetic studies

Panic disorder is a major cause of medical attention with substantial social and health service cost. Based on pharmacological studies, research on its etiopathogenesis has been focused on the possible dysfunction of specific neurotransmitter systems. However, recent work has related the genes involved in development, synaptic plasticity and synaptic remodeling to anxiety disorders. This implies that learning processes and changes in perception, interpretation and behavioral responses to environmental stimuli are essential for development of complex anxiety responses secondary to the building of specific brain neural circuits and to adult plasticity. The focus of this review is on progress achieved in identifying genes that confer increased risk for panic disorder through genetic epidemiology and the use of genetically modified mouse models. The integration of human and animal studies targeting behavioral, systems-level, cellular and molecular levels will most probably help identify new molecules with potential impact on the pathogenetic aspects of the disease.

GABAA receptors in central nervous system disease: anxiety, epilepsy, and insomnia

Brain function is based on an exquisite balance between excitatory and inhibitory neurotransmission. GABAergic neurons provide the major inhibitory control. By controlling spike timing and sculpting neuronal rhythms they play a key role in regulating behavior. GABAergic neurons are highly diverse and operate with a corresponding diversity of GABAA receptor subtypes. In this article, the contribution of GABAA receptor deficits to central nervous system disorders, in particular anxiety disorders, epilepsy, schizophrenia and insomnia, is reviewed.

Candidate gene polymorphisms in the serotonergic pathway: influence on depression symptomatology in an elderly population

BACKGROUND

Depressed mood is a major concern in the elderly, with consequences for morbidity and mortality. Previous studies have demonstrated that genetic factors in depression and subsyndromal depressive symptoms are no less important in the elderly than during other life stages. Variations in genes included in the serotonin system have been suggested as risk factors for various psychiatric disorders but may also serve as candidates for normal variations in mood.

METHODS

This study included 684 elderly Danish twins to investigate the influence of 11 polymorphisms in 7 serotonin system genes on the mean level of depression symptomatology assessed over several years, reflecting individuals' underlying mood level.

RESULTS

A suggestive association of sequence variations in genes responsible for the synthesis (TPH), recognition (5-HTR2A), and degradation (MAOA) of serotonin with depression symptomatology was found, although the effect was generally restricted to men. We also found that a specific haplotype in VMAT2, the gene encoding the vesicular monoamine transporter, was significantly associated with depression symptoms in men (p= .007).

CONCLUSIONS

These results suggest that variations in genes encoding the components of serotonin metabolism may influence the basic mood level and that different genetic factors may apply in men and women.

Neurobiology of memory and anxiety: from genes to behavior

Interaction of anxiety and memory represents an essential feature of CNS functioning. This paper reviews experimental data coming from neurogenetics, neurochemistry, and behavioral pharmacology (as well as parallel clinical findings) reflecting different mechanisms of memory-anxiety interplay, including brain neurochemistry, circuitry, pharmacology, neuroplasticity, genes, and gene-environment interactions. It emphasizes the complexity and nonlinearity of such interplay, illustrated by a survey of anxiety and learning/memory phenotypes in various genetically modified mouse models that exhibit either synergistic or reciprocal effects of the mutation on anxiety levels and memory performance. The paper also assesses the putative role of different neurotransmitter systems and neuropeptides in the regulation of memory processes and anxiety, and discusses the role of neural plasticity in these mechanisms.

Molecular heterosis in metamphetamine abusers

Objective. The aim of our study was to assess whether the catechol-O-methyltransferase (COMT) genetic background of patients dependent on metamphetamine is related to their non-abstinence in a 1-year follow-up. Methods. We examined COMT gene Val158Met polymorphism and 1-year abstinence in a group of 31 (women N=8) Czech Caucasian metamphetamine abusers (average age, 23.8±4.0years). Results. Non-abstinence was significantly (P=0.046, Fisher's exact test) associated with the heterozygous Val/Met genotype. Conclusion. The case where subjects heterozygous for a specific genetic polymorphism show a significantly greater or lesser effect for a phenotypic trait than subjects homozygous for either allele is described as molecular heterosis in the literature. We discuss several explanations and recommendations for further research.

The genetic background to PTSD

Although extensive research has already been done on the genetic bases of psychiatric disorders, little is known about polygenetic influences in posttraumatic stress disorder (PTSD). This article reviews molecular genetic studies relating to PTSD that were found in a literature search in Medline, Embase and Web of Science. Association studies have investigated 8 major genotypes in connection with PTSD. They have tested hypotheses involving key candidate genes in the serotonin (5-HTT), dopamine (DRD2, DAT), glucocorticoid (GR), GABA (GABRB), apolipoprotein systems (APOE2), brain-derived neurotrophic factor (BDNF) and neuropeptide Y (NPY). The studies have produced inconsistent results, many of which may be attributable to methodological shortcomings and insufficient statistical power. The complex aetiology of PTSD, for which experiencing a traumatic event forms a necessary condition, makes it difficult to identify specific genes that substantially contribute to the disorder. Gene-finding strategies are difficult to apply. Interactions between different genes and between them and the environment probably make certain people vulnerable to developing PTSD. Gene-environmental studies are needed that focus more narrowly on specific, distinct endophenotypes and on influences from environmental factors.

Decreased cerebrospinal fluid allopregnanolone levels in women with posttraumatic stress disorder

BACKGROUND

Alterations in the gamma-amino-butyric acid (GABA) neurotransmitter system have been identified in some populations with posttraumatic stress disorder (PTSD).

METHODS

To further investigate factors of relevance to GABAergic neurotransmission in PTSD, we measured cerebrospinal fluid (CSF) levels of allopregnanolone and pregnanolone combined (ALLO: congeners that potently and positively modulate effects of GABA at the GABA(A) receptor), 5alpha-dihydroprogesterone (5alpha-DHP: the immediate precursor for allopregnanolone), dehydroepiandrosterone (DHEA: a negative modulator of GABA(A) receptor function), and progesterone with gas chromatography, mass spectrometry in premenopausal women with (n = 9) and without (n = 10) PTSD. Subjects were free of psychotropic medications, alcohol, and illicit drugs; all were in the follicular phase of the menstrual cycle except three healthy and four PTSD subjects receiving oral contraceptives.

RESULTS

There were no group differences in progesterone, 5alpha-DHP, or DHEA levels. The PTSD group ALLO levels were < 39% of healthy group levels. The ALLO/DHEA ratio correlated negatively with PTSD re-experiencing symptoms (n = -.82, p < 008; trend) and with Profile of Mood State depression/dejection scores (n = -0.70, p < 0008).

CONCLUSION

Low CSF ALLO levels in premenopausal women with PTSD might contribute to an imbalance in inhibitory versus excitatory neurotransmission, resulting in increased PTSD re-experiencing and depressive symptoms.

Genetics of normal and pathological sleep in humans

The complexity of sleep-wake regulation, in addition to the many environmental influences, includes genetic predisposing factors, which begin to be discovered. Most of the current progress in the study of sleep genetics comes from animal models (dogs, mice, and drosophila). Multiple approaches using both animal models and different genetic techniques are needed to follow the segregation and ultimately to identify 'sleep genes' and molecular bases of sleep disorders. Recent progress in molecular genetics and the development of detailed human genome map have already led to the identification of genetic factors in several complex disorders. Only a few genes are known for which a mutation causes a sleep disorder. However, single gene disorders are rare and most common disorders are complex in terms of their genetic susceptibility, environmental factors, gene-gene, and gene-environment interactions. We review here the current progress in the genetics of normal and pathological sleep and suggest a few future perspectives.

GABA(A) receptor subtypes as targets for neuropsychiatric drug development

The main inhibitory neurotransmitter system in the brain, the gamma-aminobutyric acid (GABA) system, is the target for many clinically used drugs to treat, for example, anxiety disorders and epilepsy and to induce sedation and anesthesia. These drugs facilitate the function of pentameric A-type GABA (GABA(A)) receptors that are extremely widespread in the brain and composed from the repertoire of 19 subunit variants. Modern genetic studies have found associations of various subunit gene polymorphisms with neuropsychiatric disorders, including alcoholism, schizophrenia, anxiety, and bipolar affective disorder, but these studies are still at their early phase because they still have failed to lead to validated drug development targets. Recent neurobiological studies on new animal models and receptor subunit mutations have revealed novel aspects of the GABA(A) receptors, which might allow selective targeting of the drug action in receptor subtype-selective fashion, either on the synaptic or extrasynaptic receptor populations. More precisely, the greatest advances have occurred in the clarification of the molecular and behavioral mechanisms of action of the GABA(A) receptor agonists already in the clinical use, such as benzodiazepines and anesthetics, rather than in the introduction of novel compounds to clinical practice. It is likely that these new developments will help to overcome the present problems of the chronic treatment with nonselective GABA(A) agonists, that is, the development of tolerance and dependence, and to focus the drug action on the neurobiologically and neuropathologically relevant substrates.

Low posttrauma GABA plasma levels as a predictive factor in the development of acute posttraumatic stress disorder

BACKGROUND

Gamma amino-butyric acid (GABA) regulates the intensity and the duration of the central hyperadrenergic response in times of high stress and has been negatively associated with anxiety, depression, and sleep problems. We hypothesized that individuals with low plasma GABA levels may be more prone to develop posttraumatic stress disorder (PTSD) in the aftermath of trauma exposure.

METHODS

To test this hypothesis, we measured plasma GABA levels in a population of 108 road traffic accident victims on arrival at a traumatology department and assessed them for PTSD 6 weeks later.

RESULTS

The mean GABA level (nmol/mL) in the PTSD group (n = 55; M =.20; SD =.08) was significantly lower compared with members of the trauma-exposed group who did not develop PTSD [n = 17; M =.30; SD =.09), t(70) = 3.94, p =.0002].

CONCLUSIONS

Provided that GABA levels in the brain are genetically predetermined, our results would suggest that individuals with low plasma GABA levels are premorbidly more vulnerable to stress-related disorders such as acute PTSD. If replicated, plasma GABA levels measured in the aftermath of trauma exposure might help to identify individuals at high risk for developing PTSD.