Augmentation treatment of psychotherapy for anxiety disorders with D-cycloserine

Psychosocial impacts of caring for a child with a genetic disorder in Accra, Ghana

Caregivers caring for a child with a genetic condition may experience psychosocial distress, which may be compounded by the context in which the caring takes place. Few studies have examined psychosocial distress and support among caregivers caring for a child with a genetic disorder in low-middle-income countries such as Ghana. The purpose of the current study was to investigate the psychosocial impacts of caring for a child with a genetic disorder in an urban setting in Ghana's capital, Accra. We conducted individual interviews among 17 caregivers who were taking care of children with various genetic disorders including, albinism, Edward's syndrome, osteogenesis imperfecta, sickle cell disease, and spondyloepiphyseal dysplasia congenita. Thematic analysis of the data revealed three main themes on the psychosocial impacts, including: (1) self-blame, guilt, and shame; (2) sleep and mood disturbances; and (3) discrimination and stigmatization. We observed three themes about support: (1) psychological support; (2) family and community support; and (3) institutional support. Participants reported limited support from professionals such as psychologists. Discussion focuses on the supportive care needs of caregivers and implications for genetic counselling awareness, advocacy, and training.

Targeting NMDA Receptors in Emotional Disorders: Their Role in Neuroprotection

Excitatory glutamatergic neurotransmission mediated through N-methyl-D-Aspartate (NMDA) receptors (NMDARs) is essential for synaptic plasticity and neuronal survival. While under pathological states, abnormal NMDAR activation is involved in the occurrence and development of psychiatric disorders, which suggests a directional modulation of NMDAR activity that contributes to the remission and treatment of psychiatric disorders. This review thus focuses on the involvement of NMDARs in the pathophysiological processes of psychiatric mood disorders and analyzes the neuroprotective mechanisms of NMDARs. Firstly, we introduce NMDAR-mediated neural signaling pathways in brain function and mood regulation as well as the pathophysiological mechanisms of NMDARs in emotion-related mental disorders such as anxiety and depression. Then, we provide an in-depth summary of current NMDAR modulators that have the potential to be developed into clinical drugs and their pharmacological research achievements in the treatment of anxiety and depression. Based on these findings, drug-targeting for NMDARs might open up novel territory for the development of therapeutic agents for refractory anxiety and depression.

A perspective on molecular signalling dysfunction, its clinical relevance and therapeutics in autism spectrum disorder

Intellectual disability (ID) and autism spectrum disorder (ASD) are neurodevelopmental disorders that have become a primary clinical and social concern, with a prevalence of 2-3% in the population. Neuronal function and behaviour undergo significant malleability during the critical period of development that is found to be impaired in ID/ASD. Human genome sequencing studies have revealed many genetic variations associated with ASD/ID that are further verified by many approaches, including many mouse and other models. These models have facilitated the identification of fundamental mechanisms underlying the pathogenesis of ASD/ID, and several studies have proposed converging molecular pathways in ASD/ID. However, linking the mechanisms of the pathogenic genes and their molecular characteristics that lead to ID/ASD has progressed slowly, hampering the development of potential therapeutic strategies. This review discusses the possibility of recognising the common molecular causes for most ASD/ID based on studies from the available models that may enable a better therapeutic strategy to treat ID/ASD. We also reviewed the potential biomarkers to detect ASD/ID at early stages that may aid in diagnosis and initiating medical treatment, the concerns with drug failure in clinical trials, and developing therapeutic strategies that can be applied beyond a particular mutation associated with ASD/ID.

NMDA receptor-mediated processing in inferior frontal gyrus facilitates acquisition and extinction learning and strengthens renewal

While the renewal effect of extinction is considered to be invoked by attention to context during the extinction phase, there is also evidence that processing during initial learning (acquisition) may be important for later renewal. A noradrenergic agonist and a dopaminergic antagonist, administered before acquisition, did not affect renewal, however, the effects of NMDAergic neurotransmission in this regard are as yet unknown. In a previous study, administration of a single dose of the NMDA agonist D-cycloserine (DCS) before extinction learning facilitated extinction in the context of acquisition (AAA), but had no effect upon renewal. In the present fMRI study, DCS was administered prior to the initial acquisition of a predictive learning task, in order to investigate whether NMDA receptor (NMDAR) stimulation at this timepoint will modulate overall learning as well as the level of renewal, while increasing activation in the extinction- and renewal-relevant brain regions of inferior frontal gyrus (iFG) and hippocampus (HC). DCS facilitated acquisition, as well as extinction learning in the context of acquisition (AAA), and raised the level of ABA renewal. While BOLD activation during acquisition did not differ between treatment groups, activation in bilateral iFG showed a double dissociation during processing of AAA extinction trials, with DCS-mediated higher activation in right iFG and deactivation in left iFG. In contrast, placebo showed higher activation in left iFG and deactivation in right iFG. During the test (recall) phase, left iFG and right anterior hippocampus activation was increased in DCS participants who showed renewal, with activation in this region correlating with the ABA renewal level. The results demonstrate that NMDA receptor stimulation can facilitate both initial learning and extinction of associations, and in this way has an impact upon the resultant level of renewal. In particular NMDAergic processing in iFG appears relevant for the facilitation of AAA extinction and ABA recall in the test phase.

Parsing neural circuits of fear learning and extinction across basic and clinical neuroscience: Towards better translation

Over the past decades, studies of fear learning and extinction have advanced our understanding of the neurobiology of threat and safety learning. Animal studies can provide mechanistic/causal insights into human brain regions and their functional connectivity involved in fear learning and extinction. Findings in humans, conversely, may further enrich our understanding of neural circuits in animals by providing macroscopic insights at the level of brain-wide networks. Nevertheless, there is still much room for improvement in translation between basic and clinical research on fear learning and extinction. Through the lens of neural circuits, in this article, we aim to review the current knowledge of fear learning and extinction in both animals and humans, and to propose strategies to fill in the current knowledge gap for the purpose of enhancing clinical benefits.

Structure, Function, and Pharmacology of Glutamate Receptor Ion Channels

Many physiologic effects of l-glutamate, the major excitatory neurotransmitter in the mammalian central nervous system, are mediated via signaling by ionotropic glutamate receptors (iGluRs). These ligand-gated ion channels are critical to brain function and are centrally implicated in numerous psychiatric and neurologic disorders. There are different classes of iGluRs with a variety of receptor subtypes in each class that play distinct roles in neuronal functions. The diversity in iGluR subtypes, with their unique functional properties and physiologic roles, has motivated a large number of studies. Our understanding of receptor subtypes has advanced considerably since the first iGluR subunit gene was cloned in 1989, and the research focus has expanded to encompass facets of biology that have been recently discovered and to exploit experimental paradigms made possible by technological advances. Here, we review insights from more than 3 decades of iGluR studies with an emphasis on the progress that has occurred in the past decade. We cover structure, function, pharmacology, roles in neurophysiology, and therapeutic implications for all classes of receptors assembled from the subunits encoded by the 18 ionotropic glutamate receptor genes. SIGNIFICANCE STATEMENT: Glutamate receptors play important roles in virtually all aspects of brain function and are either involved in mediating some clinical features of neurological disease or represent a therapeutic target for treatment. Therefore, understanding the structure, function, and pharmacology of this class of receptors will advance our understanding of many aspects of brain function at molecular, cellular, and system levels and provide new opportunities to treat patients.

Randomized controlled trial of d-cycloserine in cocaine dependence: Effects on contingency management and cue-induced cocaine craving in a naturalistic setting

Cocaine dependence constitutes a significant public health concern. This randomized, double-blind, placebo-controlled trial tested a novel approach to reducing cocaine use among cocaine-dependent individuals with d-cycloserine, a drug known to enhance learning and some learning-based therapies. Urine samples and cocaine craving were assessed across three phases: induction (Weeks 1-2), treatment (Weeks 3-5; urinalysis-based contingency management plus exposure therapy), and posttreatment (Weeks 6-7). During the treatment phase, either 50 mg of d-cycloserine or placebo was administered after delivery of urinalysis feedback with potential monetary reward and before exposure therapy sessions in naturalistic contexts individually associated with cocaine use. d-cycloserine significantly improved learning on an operant laboratory task. Contingency management significantly reduced cocaine use and craving. d-cycloserine did not significantly affect cocaine use or craving in the treatment phase. Craving significantly increased for the d-cycloserine group during the post treatment phase. Therefore, although the study showed that d-cycloserine was capable of improving learning, enhancement of learning-based therapy was not observed. Moreover, no differences in behavioral measures of cocaine demand (cocaine purchasing task) or monetary or sexual delay discounting were observed across phases or between groups in any phase. These results are somewhat consistent with previous findings suggesting that d-cycloserine administration increases cocaine craving, although they differ from other findings showing that d-cycloserine administration reduces alcohol or nicotine cravings. Methodological variables (e.g., guided vs. unguided exposure therapy sessions, length of extinction exposure) likely play a role in dissimilar findings observed across studies. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Psychopharmacological Treatment of Obsessive-Compulsive Disorder (OCD)

Background:

Obsessive-compulsive disorder (OCD) is associated with affective and cognitive symptoms causing personal distress and reduced global functioning. These have considerable societal costs due to healthcare service utilization.

Objective:

Our aim was to assess the efficacy of pharmacological interventions in OCD and clinical guidelines, providing a comprehensive overview of this field.

Methods:

We searched the PubMed database for papers dealing with drug treatment of OCD, with a specific focus on clinical guidelines, treatments with antidepressants, antipsychotics, mood stabilizers, off-label medications, and pharmacogenomics.

Results:

Prolonged administration of selective serotonin reuptake inhibitors (SSRIs) is most effective. Better results can be obtained with a SSRI combined with cognitive behavioral therapy (CBT) or the similarly oriented exposure and response prevention (ERP). Refractory OCD could be treated with different strategies, including a switch to another SSRI or clomipramine, or augmentation with an atypical antipsychotic. The addition of medications other than antipsychotics or intravenous antidepressant administration needs further investigation, as the evidence is inconsistent. Pharmacogenomics and personalization of therapy could reduce treatment resistance.

Conclusions:

SSRI/clomipramine in combination with CBT/ERP is associated with the optimal response compared to each treatment alone or to other treatments. New strategies for refractory OCD are needed. The role of pharmacogenomics could become preponderant in the coming years.

Exposure and Response Prevention in the Treatment of Obsessive-Compulsive Disorder: Current Perspectives

Numerous clinical trials support the efficacy of exposure and response prevention (ERP) for the treatment of obsessive-compulsive disorder (OCD). Accordingly, ERP has been formally recognized as a first-line, evidence-based treatment for OCD. This review discusses the theoretical underpinnings of the treatment from a behavioral and neurobiological perspective and summarizes the evidence supporting the efficacy of ERP across child and adult populations. Next, we discuss predictors of ERP treatment outcome and discuss implementation strategies designed to improve feasibility and adoption. Finally, strategies to improve treatment dissemination are discussed.

D-Cycloserine Facilitates Reversal in an Animal Model of Post-traumatic Stress Disorder

Many psychiatric disorders are associated with cognitive dysfunction that is ineffectively treated by existing pharmacotherapies and which may contribute to poor real-world functioning. D-cycloserine (DCS) is a partial N-methyl-D-aspartate (NMDA) agonist that has attracted attention because of its cognitive enhancing properties, including in people with post-traumatic stress disorder (PTSD). Here, we examined the effect of DCS on reversal learning - a type of cognitive flexibility - following exposure to single prolonged stress (SPS), a rodent model of PTSD. Male Sprague Dawley rats (n = 64) were trained to press levers in an operant chamber, matched for performance and assigned to SPS or control (unstressed) groups. Following SPS, rats received three additional lever press sessions, followed by a side bias test on day three. One day later they learned a response discrimination rule (press left or right lever, opposite to side bias) and on a subsequent day were trained (and tested) for reversal to the opposite lever. DCS (15 mg/kg) or vehicle was administered 30 minutes prior to the reversal session. No between-group differences were found in acquisition or retrieval of the initial rule, but a significant drug x stress interaction on response discrimination reversal indicated that DCS had a greater beneficial effect on SPS rats' cognitive flexibility than it did on performance in controls. These findings add to a growing literature on the beneficial effects of DCS for treating a wide variety of deficits that develop following exposure to extreme stress and may have implications for the development of novel pharmacotherapies for PTSD.

D-cycloserine improves synaptic transmission in an animal model of Rett syndrome

Rett syndrome (RTT), a leading cause of intellectual disability in girls, is predominantly caused by mutations in the X-linked gene MECP2. Disruption of Mecp2 in mice recapitulates major features of RTT, including neurobehavioral abnormalities, which can be reversed by re-expression of normal Mecp2. Thus, there is reason to believe that RTT could be amenable to therapeutic intervention throughout the lifespan of patients after the onset of symptoms. A common feature underlying neuropsychiatric disorders, including RTT, is altered synaptic function in the brain. Here, we show that Mecp2^tm1.1Jae/y mice display lower presynaptic function as assessed by paired pulse ratio, as well as decreased long term potentiation (LTP) at hippocampal Schaffer–collateral-CA1 synapses. Treatment of Mecp2^tm1.1Jae/y mice with D-cycloserine (DCS), an FDA-approved analog of the amino acid D-alanine with antibiotic and glycinergic activity, corrected the presynaptic but not LTP deficit without affecting deficient hippocampal BDNF levels. DCS treatment did, however, partially restore lower BDNF levels in the brain stem and striatum. Thus, treatment with DCS may mitigate the severity of some of the neurobehavioral symptoms experienced by patients with Rett syndrome.

The Efficacy of Augment of D-Cycloserine and Cognitive-behavioral Therapy on Adolescent with one Type of Anxiety Disorders: A Double-blind Randomized Controlled Trial

Background:

This study was designed to investigating the effect of combining D-cycloserine (DCS) and cognitive-behavioral therapy (CBT) on adolescent with at least one type of anxiety disorders.

Materials and Methods:

The present study was conducted as a double-blind randomized controlled trial on 36 adolescent with anxiety disorders. Patients were assessed in two groups. In addition to 4 sessions of weekly CBT in both groups; case group, received a 50-mg DCS capsules, control group, received Placebo daily for a month. Patients received DCS capsules or placebo 1 h before sessions of CBT. Age, sex, kind of anxiety disorders “screen for child anxiety related disorders (SCARED)” and “cognitive abilities test (CATS)” scores were evaluated and compared between groups.

Results:

The mean age of the studied patients (29 females (80.6%) and 7 males (19.4%)) was 14.1 ± 1.8 years. The most frequent anxiety disorder among the study population was generalized social disorder (GAD) (77.7%). Age, sex and the frequency of anxiety disorders were not statistically significant between the study groups (P > 0.05). The mean score of “SCARED” and “CATS” at before starting the treatment, after treatment and three month after the treatment were not statistically significant between groups (P > 0.05). Also, decrease in values of “SCARED” and “CATS” during the evaluation time periods was not statistically significant between groups (P > 0.05).

Conclusions:

Findings of this study showed that there has been no difference in symptoms improvement in adolescent with anxiety disorder who received treatment protocol including 4 sessions of CBT, weekly, together with 50 mgs of DCS compared to the patients of the control group.

The role of basal forebrain cholinergic neurons in fear and extinction memory

Cholinergic input to the neocortex, dorsal hippocampus (dHipp), and basolateral amygdala (BLA) is critical for neural function and synaptic plasticity in these brain regions. Synaptic plasticity in the neocortex, dHipp, ventral Hipp (vHipp), and BLA has also been implicated in fear and extinction memory. This finding raises the possibility that basal forebrain (BF) cholinergic neurons, the predominant source of acetylcholine in these brain regions, have an important role in mediating fear and extinction memory. While empirical studies support this hypothesis, there are interesting inconsistencies among these studies that raise questions about how best to define the role of BF cholinergic neurons in fear and extinction memory. Nucleus basalis magnocellularis (NBM) cholinergic neurons that project to the BLA are critical for fear memory and contextual fear extinction memory. NBM cholinergic neurons that project to the neocortex are critical for cued and contextual fear conditioned suppression, but are not critical for fear memory in other behavioral paradigms and in the inhibitory avoidance paradigm may even inhibit contextual fear memory formation. Medial septum and diagonal band of Broca cholinergic neurons are critical for contextual fear memory and acquisition of cued fear extinction. Thus, even though the results of previous studies suggest BF cholinergic neurons modulate fear and extinction memory, inconsistent findings among these studies necessitates more research to better define the neural circuits and molecular processes through which BF cholinergic neurons modulate fear and extinction memory. Furthermore, studies determining if BF cholinergic neurons can be manipulated in such a manner so as to treat excessive fear in anxiety disorders are needed.

Randomized, Placebo-Controlled, Double-Blind Pilot Study of D-Cycloserine in Chronic Stroke

Stroke is a leading cause of death and disability in the USA. Up to 60% of patients do not fully recover despite intensive physical therapy treatment. N-Methyl-D-aspartate receptors (NMDA-R) have been shown to play a role in synaptic plasticity when activated. D-Cycloserine promotes NMDA receptor function by binding to receptors with unoccupied glycine sites. These receptors are involved in learning and memory. We hypothesized that D-cycloserine, when combined with robotic-assisted physiotherapy (RAP), would result in greater gains compared with placebo + RAP in stroke survivors. Participants (n = 14) were randomized to D-cycloserine plus RAP or placebo plus RAP. Functional, cognitive, and quality-of-life measures were used to assess recovery. There was significant improvement in grip strength of the affected hand within both groups from baseline to 3 weeks (95% confidence interval for mean change, 3.95 ± 2.96 to 4.90 ± 3.56 N for D-cycloserine and 5.72 ± 3.98 to 8.44 ± 4.90 N for control). SIS mood domain showed improvement for both groups (95% confidence interval for mean change, 72.6 ± 16.3 to 82.9 ± 10.9 for D-cycloserine and 82.9 ± 13.5 to 90.3 ± 9.9 for control). This preliminary study does not provide evidence that D-cycloserine can provide greater gains in learning compared with placebo for stroke survivors.

D-cycloserine augmentation in behavioral therapy for obsessive-compulsive disorder: a meta-analysis

OBJECTIVE

To evaluate the overall effect of D-cycloserine (DCS) augmentation on exposure and response prevention (ERP) therapy for obsessive-compulsive disorder (OCD).

METHODS

Clinical studies on the effect of DCS augmentation on ERP therapy for OCD compared to placebo were included for meta analysis. The primary outcome was the Yale-Brown Obsessive-Compulsive Scale (Y-BOCS). Meta-analyses were performed with a random-effect model or a fixed-effect model using the Cochrane Review Manager (RevMan, version 5.2) to calculate the odds ratio and the mean difference, with their corresponding 95% confidence intervals.

RESULTS

A total of six studies was included in the current meta-analyses, and their data were extracted. Among them, four were for analyses of DCS and Y-BOCS at midtreatment, six for analysis at posttreatment, and four at 3-month follow-up. Besides, three of the six eligible studies were included in the meta-analysis of the DCS and Clinical Global Impression-Severity Scale at posttreatment, and three in the meta-analysis of DCS and proportions of treatment responders and of subjects attaining clinical remission status criteria at posttreatment. Our meta-analyses do not reveal a significant effect of DCS augmentation in ERP therapy for OCD patients, except when measured at midtreatment. Compared to the placebo group, DCS augmentation did show a trend toward significantly lower/decreased Y-BOCS; when measured at posttreatment and in the subpopulation of DCS taken before some of the ERP sessions, DCS augmentation showed a trend toward significantly lower/decreased Y-BOCS.

CONCLUSION

Our result suggested that with the careful optimization of DCS-augmented ERP therapy by fine-tuning timing and dosing of DCS administration and number and frequency of ERP sessions, DCS may enhance the efficacy of ERP therapy in reducing the symptomatic severity of OCD patients, especially at early stage of the treatment; therefore, DCS augmentation could possibly reduce treatment cost, reduce treatment drop and refusal rate, and help to improve access to the limited number of experienced therapists.

A selective review of glutamate pharmacological therapy in obsessive-compulsive and related disorders

Glutamate, an excitatory central nervous system neurotransmitter, is emerging as a potential alternative pharmacological treatment when compared to gamma-aminobutyric acid (GABA)-, dopamine-, and serotonin-modulating treatments for neuropsychiatric conditions. The pathophysiology, animal models, and clinical trials of glutamate modulation are explored in disorders with underlying inhibitory deficits (cognitive, motor, behavioral) including obsessive–compulsive disorder, attention deficit hyperactivity disorder, Tourette syndrome, trichotillomania, excoriation disorder, and nail biting. Obsessive–compulsive disorder, attention deficit hyperactivity disorder, and grooming disorders (trichotillomania and excoriation disorder) have emerging positive data, although only scarce controlled trials are available. The evidence is less supportive for the use of glutamate modulators in Tourette syndrome. Glutamate-modulating agents show promise in the treatment of disorders of inhibition.

The fear of food measure: a novel measure for use in exposure therapy for eating disorders

OBJECTIVE

Exposure therapy for mealtime anxiety has preliminarily been effective at increasing food intake and decreasing anxiety in individuals with anorexia nervosa (AN). To enhance our knowledge of exposure therapy for AN researchers and clinicians need a comprehensive measure that assesses outcomes relevant to exposure therapy for AN.

METHOD

In the current four studies we developed Fear of Food Measure (FOFM) that assesses three cognitive and behavioral outcomes: trait anxiety about eating, food avoidance behaviors, and feared concerns related to eating.

RESULTS

In a community (N = 399) and undergraduate female sample (N = 203) the FOFM exhibited a good three-factor structure and convergent and divergent validity. In a sample of women (N = 72) we showed that the anxiety about eating subscale significantly predicted in vivo food intake over and above other established predictors of eating (e.g., restraint). In a clinical sample diagnosed with an eating disorder (N = 41) we showed that anxiety about eating was associated with food intake and anxiety during an exposure meal and that all subscales of the FOFM significantly decreased over the course of a four-session exposure intervention. Finally, we found that participants diagnosed with an eating disorder had higher levels of fear of food than did matched controls (N = 23).

DISCUSSION

The FOFM is a psychometrically valid measure that can assess if patients are improving while undergoing exposure therapy and could be used to pinpoint problematic behaviors that can be addressed in exposure therapy.

Tau-mediated NMDA receptor impairment underlies dysfunction of a selectively vulnerable network in a mouse model of frontotemporal dementia

Frontotemporal dementia (FTD) is a neurodegenerative behavioral disorder that selectively affects the salience network, including the ventral striatum and insula. Tau mutations cause FTD, but how mutant tau impairs the salience network is unknown. Here, we address this question using a mouse model expressing the entire human tau gene with an FTD-associated mutation (V337M). Mutant, but not wild-type, human tau transgenic mice had aging-dependent repetitive and disinhibited behaviors, with synaptic deficits selectively in the ventral striatum and insula. There, mutant tau depleted PSD-95, resulting in smaller postsynaptic densities and impaired synaptic localization of NMDA receptors (NMDARs). In the ventral striatum, decreased NMDAR-mediated transmission reduced striatal neuron firing. Pharmacologically enhancing NMDAR function with the NMDAR co-agonist cycloserine reversed electrophysiological and behavioral deficits. These results indicate that NMDAR hypofunction critically contributes to FTD-associated behavioral and electrophysiological alterations and that this process can be therapeutically targeted by a Food and Drug Administration-approved drug.

Social cognition

Social cognition is a major problem underlying deficiencies in interpersonal relationships in several psychiatric populations. And yet there is currently no gold standard for pharmacological treatment of psychiatric illness that directly targets these social cognitive areas. This chapter serves to illustrate some of the most innovative attempts at pharmacological modulation of social cognition in psychiatric illnesses including schizophrenia, borderline personality disorder, autism spectrum disorders, antisocial personality disorder and psychopathy, social anxiety disorder, and posttraumatic stress disorder. Pharmacological modulation includes studies administering oxytocin, ecstasy (MDMA), modafinil, methylphenidate, and D-cycloserine. Furthermore, some background on social cognition research in healthy individuals, which could be helpful in developing future treatments, is provided as well as the potential for each drug as a long-term treatment option.

The CRF₁ receptor antagonist SSR125543 prevents stress-induced long-lasting sleep disturbances in a mouse model of PTSD: comparison with paroxetine and d-cycloserine

The selective CRF₁ (corticotropin releasing factor type 1) receptor antagonist SSR125543 has been previously shown to attenuate the long-term behavioral and electrophysiological effects produced by traumatic stress exposure in mice. Sleep disturbances are one of the most commonly reported symptoms by people with post-traumatic stress disorder (PTSD). The present study aims at investigating whether SSR125543 (10 mg/kg/day/i.p. for 2 weeks) is able to attenuate sleep/wakefulness impairment induced by traumatic stress exposure in a model of PTSD in mice using electroencephalographic (EEG) analysis. Effects of SSR125543 were compared to those of the 5-HT reuptake inhibitor, paroxetine (10 mg/kg/day/i.p.), and the partial N-methyl-d-aspartate (NMDA) receptor agonist, d-cycloserine (10 mg/kg/day/i.p.), two compounds which have demonstrated clinical efficacy against PTSD. Baseline EEG recording was performed in the home cage for 6h prior to the application of two electric foot-shocks of 1.5 mA. Drugs were administered from day 1 post-stress to the day preceding the second EEG recording session, performed 14 days later. Results showed that at day 14 post-stress, shocked mice displayed sleep fragmentation as shown by an increase in the occurrence of both non-rapid eye movement (NREM) sleep and wakefulness bouts. The duration of wakefulness, NREM and REM sleep were not significantly affected. The stress-induced effects were prevented by repeated administration of SSR125543, paroxetine and D-cycloserine. These findings confirm further that the CRF₁ receptor antagonist SSR125543 is able to attenuate the deleterious effects of traumatic stress exposure.

Endogenous cortisol levels influence exposure therapy in spider phobia

Previous research in patients with phobia showed that the administration of glucocorticoids reduces fear in phobic situations and enhances exposure therapy. Glucocorticoids underlie a daily cycle with a peak in the morning and low levels during the evening and night. The aim of the present study was to investigate whether exposure is more effective when conducted in the morning when endogenous cortisol levels are high. Sixty patients meeting DSM IV criteria for specific phobia (animal type) were randomly assigned to one-session exposure treatment either at 08.00 a.m. (high cortisol group) or at 06.00 p.m. (low cortisol group). Participants returned for a posttreatment assessment one week after therapy and a follow-up assessment three months after therapy. Both groups showed good outcome, but patients treated in the morning exhibited significantly less fear of spiders in the behavioral approach test (BAT) and a trend for lower scores on the Fear of Spiders Questionnaire (FSQ) than patients treated in the evening. This effect was present at posttreatment and follow-up. Our findings indicate that exposure therapy is more effective in the morning than in the evening. We suggest that this may be due to higher endogenous cortisol levels in the morning group that enhance extinction memory.

Does D-cycloserine enhance exposure therapy for anxiety disorders in humans? A meta-analysis

The treatment of anxiety is on the edge of a new era of combinations of pharmacologic and psychosocial interventions. A new wave of translational research has focused on the use of pharmacological agents as psychotherapy adjuvants using neurobiological insights into the mechanism of the action of certain psychological treatments such as exposure therapy. Recently, d-cycloserine (DCS) an antibiotic used to treat tuberculosis has been applied to enhance exposure-based treatment for anxiety and has proved to be a promising, but as yet unproven intervention. The present study aimed to evaluate the efficacy of DCS in the enhancement of exposure therapy in anxiety disorders. A systematic review/meta-analysis was conducted. Electronic searches were conducted in the databases ISI-Web of Science, Pubmed and PsycINFO. We included only randomized, double-blind, placebo-controlled trials with humans, focusing on the role of DCS in enhancing the action of exposure therapy for anxiety disorders. We identified 328 references, 13 studies were included in our final sample: 4 on obsessive-compulsive disorder, 2 on panic disorder, 2 on social anxiety disorder, 2 on posttraumatic stress disorder, one on acrophobia, and 2 on snake phobia. The results of the present meta-analysis show that DCS enhances exposure therapy in the treatment of anxiety disorders (Cohen d =  −0.34; CI: −0.54 to −0.14), facilitating the specific process of extinction of fear. DCS seems to be effective when administered at a time close to the exposure therapy, at low doses and a limited number of times. DCS emerges as a potential new therapeutic approach for patients with refractory anxiety disorders that are unresponsive to the conventional treatments available. When administered correctly, DCS is a promising strategy for augmentation of CBT and could reduce health care costs, drop-out rates and bring faster relief to patients.

No evidence for enhanced extinction memory consolidation through noradrenergic reuptake inhibition-delayed memory test and reinstatement in human fMRI

RATIONALE

One promising approach in the current ambition to maximise treatment benefit for anxiety disorders is the pharmacological enhancement of cognitive-behavioural treatment efficacy, which can be experimentally modelled by pharmacological enhancement of extinction learning/consolidation. Noradrenaline (NA) is involved in memory consolidation, and NAergic innervations are found in brain areas implicated in fear conditioning and extinction.

OBJECTIVES

Thus, to enhance extinction memory consolidation through boosted NAergic signalling, we administered 4 mg reboxetine (RBX) immediately after extinction learning (day 2, 24 h after conditioning on day 1) in a randomised, placebo (PLC)-controlled design. At a delayed memory test (day 8), we probed cued and contextual fear and extinction memories before and after a reinstatement manipulation.

RESULTS

After reinstatement, we find significantly enhanced amygdala and posterior hippocampus activation in the RBX group, areas implicated in fear memory expression, while the PLC group exhibited enhanced activation in areas associated with extinction memory expression (vmPFC, anterior hippocampus). No group differences were found in skin conductance responses.

CONCLUSIONS

Thus, our data do not support our hypothesis that enhancement of NA signalling may facilitate extinction memory consolidation and provide preliminary evidence that this might rather enhance fear memories on a neural but not physiological (skin conductance responses) level.

The effect of acutely administered MDMA on subjective and BOLD-fMRI responses to favourite and worst autobiographical memories

3,4-methylenedioxymethamphetamine (MDMA) is a potent monoamine-releaser that is widely used as a recreational drug. Preliminary work has supported the potential of MDMA in psychotherapy for post-traumatic stress disorder (PTSD). The neurobiological mechanisms underlying its putative efficacy are, however, poorly understood. Psychotherapy for PTSD usually requires that patients revisit traumatic memories, and it has been argued that this is easier to do under MDMA. Functional magnetic resonance imaging (fMRI) was used to investigate the effect of MDMA on recollection of favourite and worst autobiographical memories (AMs). Nineteen participants (five females) with previous experience with MDMA performed a blocked AM recollection (AMR) paradigm after ingestion of 100 mg of MDMA-HCl or ascorbic acid (placebo) in a double-blind, repeated-measures design. Memory cues describing participants' AMs were read by them in the scanner. Favourite memories were rated as significantly more vivid, emotionally intense and positive after MDMA than placebo and worst memories were rated as less negative. Functional MRI data from 17 participants showed robust activations to AMs in regions known to be involved in AMR. There was also a significant effect of memory valence: hippocampal regions showed preferential activations to favourite memories and executive regions to worst memories. MDMA augmented activations to favourite memories in the bilateral fusiform gyrus and somatosensory cortex and attenuated activations to worst memories in the left anterior temporal cortex. These findings are consistent with a positive emotional-bias likely mediated by MDMA's pro-monoaminergic pharmacology.

Combining d-cycloserine with motor training does not result in improved general motor learning in neurologically intact people or in people with stroke

Neurological rehabilitation involving motor training has resulted in clinically meaningful improvements in function but is unable to eliminate many of the impairments associated with neurological injury. Thus there is a growing need for interventions that facilitate motor learning during rehabilitation therapy, to optimize recovery. d-Cycloserine (DCS), a partial N-methyl-d-aspartate (NMDA) receptor agonist that enhances neurotransmission throughout the central nervous system (Ressler KJ, Rothbaum BO, Tannenbaum L, Anderson P, Graap K, Zimand E, Hodges L, Davis M. Arch Gen Psychiatry 61: 1136-1144, 2004), has been shown to facilitate declarative and emotional learning. We therefore tested whether combining DCS with motor training facilitates motor learning after stroke in a series of two experiments. Forty-one healthy adults participated in experiment I, and twenty adults with stroke participated in experiment II of this two-session, double-blind study. Session one consisted of baseline assessment, subject randomization, and oral administration of DCS or placebo (250 mg). Subjects then participated in training on a balancing task, a simulated feeding task, and a cognitive task. Subjects returned 1-3 days later for posttest assessment. We found that all subjects had improved performance from pretest to posttest on the balancing task, the simulated feeding task, and the cognitive task. Subjects who were given DCS before motor training, however, did not show enhanced learning on the balancing task, the simulated feeding task, or the associative recognition task compared with subjects given placebo. Moreover, training on the balancing task did not generalize to a similar, untrained balance task. Our findings suggest that DCS does not enhance motor learning or motor skill generalization in neurologically intact adults or in adults with stroke.

Does change in distress matter? Mechanisms of change in prolonged exposure for PTSD

BACKGROUND AND OBJECTIVES

Clinically, many individuals persist in prolonged exposure therapy (PE) for chronic PTSD despite continuing distress during recounting of the trauma memory (imaginal exposure). Theorists suggest that distress reduction is necessary for successful treatment outcome (e.g., Foa & Kozak, 1986), while others suggest otherwise (e.g., Craske et al., 2008). This study examined clinically reliable changes in distress, relations to broad clinical outcomes, and whether homework adherence affected this relationship.

METHOD

In 116 patients with PTSD, first to last imaginal exposure sessions' peak and average distress was examined, calculating reliable change in distress. Homework adherence and helpfulness were examined. At post-treatment, PTSD symptoms (re-experiencing, avoidance, hyperarousal), depression, and functioning were examined.

RESULTS

Patients exhibited a lack of reliable change in distress (64.7%) more than a reliable change in distress (35.3%). Although no difference in post-treatment PTSD diagnostic status, individuals experiencing a reliable change in distress reported lower PTSD severity (re-experiencing, hyperarousal), depression, and better functioning. Further, perceived helpfulness of imaginal homework had an indirect effect on this relationship.

LIMITATIONS

This study did not utilize a distress tolerance self-report measure; however, examined self-reported distress during imaginal exposure.

CONCLUSIONS

Results are encouraging for clinicians treating PTSD with PE, arguing that lack of reliable change in distress to the trauma memory does not result in treatment failure. Patient "buy in" to homework, rather than amount completed, was related to the process of distress reduction. Results suggest that distress reduction in imaginal exposure is not a key mechanism underlying therapeutic change in PE.

The role of the medial prefrontal cortex in regulating social familiarity-induced anxiolysis

Overcoming specific fears and subsequent anxiety can be greatly enhanced by the presence of familiar social partners, but the neural circuitry that controls this phenomenon remains unclear. To overcome this, the social interaction (SI) habituation test was developed in this lab to systematically investigate the effects of social familiarity on anxiety-like behavior in rats. Here, we show that social familiarity selectively reduced anxiety-like behaviors induced by an ethological anxiogenic stimulus. The anxiolytic effect of social familiarity could be elicited over multiple training sessions and was specific to both the presence of the anxiogenic stimulus and the familiar social partner. In addition, socially familiar conspecifics served as a safety signal, as anxiety-like responses returned in the absence of the familiar partner. The expression of the social familiarity-induced anxiolysis (SFiA) appears dependent on the prefrontal cortex (PFC), an area associated with cortical regulation of fear and anxiety behaviors. Inhibition of the PFC, with bilateral injections of the GABAA agonist muscimol, selectively blocked the expression of SFiA while having no effect on SI with a novel partner. Finally, the effect of D-cycloserine, a cognitive enhancer that clinically enhances behavioral treatments for anxiety, was investigated with SFiA. D-cycloserine, when paired with familiarity training sessions, selectively enhanced the rate at which SFiA was acquired. Collectively, these outcomes suggest that the PFC has a pivotal role in SFiA, a complex behavior involving the integration of social cues of familiarity with contextual and emotional information to regulate anxiety-like behavior.

Treatment of pediatric anxiety disorders

This article provides a brief review of the current available data concerning present treatment and potential new treatment advances for pediatric anxiety disorders, such as generalized anxiety disorder, separation anxiety disorder, social phobia, obsessive-compulsive disorder, and posttraumatic stress disorder. Disorder-specific treatment methods and innovations, particularly computer-assisted methods of delivery for cognitive behavioral therapy (CBT) will be reviewed. Additionally, the paper will discuss novel psychopharmacological compounds (e.g., D-cycloserine, riluzole, memantine, and anticonvulsant medications). Available evidence for the efficacy of novel medication strategies in adult studies and implications for their use in pediatrics will be discussed.

The Future of D-Cycloserine and Other Cognitive Modifiers in Obsessive-Compulsive and Related Disorders

Variants of exposure therapy are effective for treating obsessive-compulsive and related disorders (OCRDs). However, significant numbers of patients do not respond adequately to exposure therapy resulting in continued distress and functional impairment. Therefore, novel approaches to augmenting exposure therapy are needed to adequately treat non- and partial-responders. Emerging research suggests that interventions that augment learning and memory processes associated with exposure therapy (i.e., extinction training) may display promise in enhancing treatment response in OCRDs. As the most studied example, d-cycloserine (DCS) is a relatively safe cognitive enhancer that appears to accelerate treatment gains associated with exposure therapy. This article reviews research on the use of DCS and other putative cognitive modifiers as they relate to the treatment (or prospective treatment) of obsessive-compulsive disorder and other OCRDs.

Impact of DCS-facilitated cue exposure therapy on brain activation to cocaine cues in cocaine dependence

BACKGROUND

The development of addiction is marked by a pathological associative learning process that imbues incentive salience to stimuli associated with drug use. Recent efforts to treat addiction have targeted this learning process using cue exposure therapy augmented with d-cycloserine (DCS), a glutamatergic agent hypothesized to enhance extinction learning. To better understand the impact of DCS-facilitated extinction on neural reactivity to drug cues, the present study reports fMRI findings from a randomized, double-blind, placebo-controlled trial of DCS-facilitated cue exposure for cocaine dependence.

METHODS

Twenty-five participants completed two MRI sessions (before and after intervention), with a cocaine-cue reactivity fMRI task. The intervention consisted of 50mg of DCS or placebo, combined with two sessions of cocaine cue exposure and skills training.

RESULTS

Participants demonstrated cocaine cue activation in a variety of brain regions at baseline. From the pre- to post-study scan, participants experienced decreased activation to cues in a number of regions (e.g., accumbens, caudate, frontal poles). Unexpectedly, placebo participants experienced decreases in activation to cues in the left angular and middle temporal gyri and the lateral occipital cortex, while DCS participants did not.

CONCLUSIONS

Three trials of DCS-facilitated cue exposure therapy for cocaine dependence have found that DCS either increases or does not significantly impact response to cocaine cues. The present study adds to this literature by demonstrating that DCS may prevent extinction to cocaine cues in temporal and occipital brain regions. Although consistent with past research, results from the present study should be considered preliminary until replicated in larger samples.

D-cycloserine augmentation of cognitive behavioral group therapy of social anxiety disorder: prognostic and prescriptive variables

OBJECTIVE

The aim of the current study was to identify individual characteristics that (a) predict symptom improvement with group cognitive behavioral therapy (CBT) for social anxiety disorder (SAD; i.e., prognostic variables) or (b) moderate the effects of d-cycloserine (DCS) versus placebo augmentation of CBT for SAD (i.e., prescriptive variables).

METHOD

Adults with SAD (N = 169) provided Liebowitz Social Anxiety Scale scores in a trial evaluating DCS augmentation of group CBT. Rate of symptom improvement during therapy and posttreatment symptom severity were evaluated using multilevel modeling. As predictors of these 2 parameters, we selected the range of variables assessed at baseline (demographic characteristics, clinical characteristics, personality traits). Using step-wise analyses, we first identified prognostic and prescriptive variables within each of these domains and then entered these significant predictors simultaneously in 1 final model.

RESULTS

African American ethnicity and cohabitation status were associated with greater overall rates of improvement during therapy and lower posttreatment severity. Higher initial severity was associated with a greater improvement during therapy but also higher posttreatment severity (the greater improvement was not enough to overcome the initial higher severity). DCS augmentation was evident only among individuals low in conscientiousness and high in agreeableness.

CONCLUSIONS

African American ethnicity, cohabitation status, and initial severity are prognostic of favorable CBT outcomes in SAD. DCS augmentation appears particularly useful for patients low in conscientiousness and high in agreeableness. These findings can guide clinicians in making decisions about treatment strategies and can help direct research on the mechanisms of these treatments.

Difficult-to-treat pediatric obsessive-compulsive disorder: feasibility and preliminary results of a randomized pilot trial of D-cycloserine-augmented behavior therapy

BACKGROUND

This study examined the feasibility and preliminary effectiveness of d-cycloserine (DCS)-augmented cognitive behavioral therapy (CBT) for children and adolescents with difficult-to-treat Obsessive Compulsive Disorder, in a double-blind randomized controlled pilot trial (RCT).

METHODS

Seventeen children and adolescents (aged 8-18 years) with a primary diagnosis of OCD, which was deemed difficult-to-treat, were randomly assigned to either nine sessions of CBT including five sessions of DCS-augmented exposure and response prevention (ERP) [ERP + DCS] or nine sessions of CBT including five sessions of placebo-augmented ERP [ERP + PBO]. Weight-dependent DCS or placebo doses (25 or 50 mg) were taken 1 hour before ERP sessions.

RESULTS

At posttreatment, both groups showed significant improvements with 94% of the entire sample classified as responders. However, a greater improvement in the ERP + DCS relative to the ERP + PBO condition was observed at 1-month follow-up on clinician-rated obsessional severity and diagnostic severity, and parent ratings of OCD severity. There were no changes across time or condition from 1- to 3-month follow-up.

CONCLUSIONS

In this preliminary study, DCS-augmented ERP produced significant improvements in OCD severity from posttreatment to 1-month follow-up, relative to a placebo control condition, in severe and difficult-to-treat pediatric OCD. The significant effect on obsessional severity suggests that DCS augmentation might be associated with enhanced modification of obsessional thoughts during ERP, and warrants further investigation.

Effect of D-cycloserine in conjunction with fear extinction training on extracellular signal-regulated kinase activation in the medial prefrontal cortex and amygdala in rat

D-cycloserine (DCS) is currently under clinical trials for a number of neuropsychiatric conditions and has been found to augment fear extinction in rodents and exposure therapy in humans. However, the molecular mechanism of DCS action in these multiple modalities remains unclear. Here, we describe the effect of DCS administration, alone or in conjunction with extinction training, on neuronal activity (c-fos) and neuronal plasticity [phospho-extracellular signal-regulated kinase (pERK)] markers using immunohistochemistry. We found that intraperitoneal administration of DCS in untrained young rats (24-28 days old) increased c-fos- and pERK-stained neurons in both the prelimbic and infralimbic division of the medial prefrontal cortex (mPFC) and reduced pERK levels in the lateral nucleus of the central amygdala. Moreover, DCS administration significantly increased GluA1, GluN1, GluN2A, and GluN2B expression in the mPFC. In a separate set of animals, we found that DCS facilitated fear extinction and increased pERK levels in the infralimbic prefrontal cortex, prelimbic prefrontal cortex intercalated cells and lateral nucleus of the central amygdala, compared with saline control. In the synaptoneurosomal preparation, we found that extinction training increased iGluR protein expression in the mPFC, compared with context animals. No significant difference in protein expression was observed between extinction-saline and extinction-DCS groups in the mPFC. In contrast, in the amygdala DCS, the conjunction with extinction training led to an increase in iGluR subunit expression, compared with the extinction-saline group. Our data suggest that the efficacy of DCS in neuropsychiatric disorders may be partly due to its ability to affect neuronal activity and signaling in the mPFC and amygdala subnuclei.

The science of cognitive therapy

Cognitive therapy (CT) refers to a family of interventions and a general scientific approach to psychological disorders. This family has evolved from a specific treatment model into a scientific approach that incorporates a wide variety of disorder-specific interventions and treatment techniques. The goal of this article is to describe the scientific approach of CT, review the efficacy and validity of the CT model, and exemplify important differences and commonalities of the CT approaches based on two specific disorders, posttraumatic stress disorder and health anxiety.

A randomized, placebo-controlled laboratory study of the effects of D-cycloserine on craving in cocaine-dependent individuals

RATIONALE

D-Cycloserine (DCS), a partial glutamate N-methyl-D-aspartate (NMDA) receptor agonist, enhances extinction of conditioned fear responding; preliminary data suggest that it may facilitate extinction of drug cue reactivity.

OBJECTIVE

This study investigates DCS effects on cocaine cue craving and drug use in cocaine-dependent subjects.

METHODS

Thirty-two subjects were randomly assigned to receive (1) DCS only, (2) DCS before sessions 1 and 3, placebo (PBO) before session 2, or (3) PBO only 15-min before each of 3 1-h cocaine cue exposure sessions conducted 1 day apart. Craving ratings were obtained before, during, and after sessions. Drug use and cue-induced craving were assessed 1 week after the last cue session.

RESULTS

Repeated presentation of cocaine cues resulted in decreased craving both within and between sessions. DCS did not facilitate extinction learning and may have enhanced craving. The group that received three doses of DCS had significantly higher craving than the PBO group at the baseline ratings taken before sessions 2 and 3, as well as significantly higher cue-induced craving at follow-up. The group that received two doses of DCS did not differ from the PBO group. There were no group differences in postextinction cocaine use.

CONCLUSIONS

The reduction of cocaine cue reactivity in the PBO group suggests that the study procedures were sufficient to produce extinction. Under these conditions, DCS did not facilitate extinction and may have enhanced craving. Further studies of glutamatergic agents and extinction in cocaine dependence should include consideration of procedural variables that could have a major impact on study outcomes.

Novel NMDA receptor modulators: an update

INTRODUCTION

The NMDA receptor is a ligand-gated ion channel that plays a critical role in higher level brain processes and has been implicated in a range of neurological and psychiatric conditions. Although initial studies for the use of NMDA receptor antagonists in neuroprotection were unsuccessful, more recently, NMDA receptor antagonists have shown clinical promise in other indications such as Alzheimer's disease, Parkinson's disease, pain and depression. Based on the clinical observations and more recent insights into receptor pharmacology, new modulatory approaches are beginning to emerge, with potential therapeutic benefit.

AREAS COVERED

The article covers the known pharmacology and important features regarding NMDA receptors and their function. A discussion of pre-clinical and clinical relevance is included, as well. The subsequent patent literature review highlights the current state of the art targeting the receptor since the last review in 2010.

EXPERT OPINION

The complex nature of the NMDA receptor structure and function is becoming better understood. As knowledge about this receptor increases, it opens up new opportunities for targeting the receptor for many therapeutic indications. New strategies and advances in older technologies will need to be further developed before clinical success can be achieved. First-in-class potentiators and subunit-selective agents form the basis for most new strategies, complemented by efforts to limit off-target liability and fine-tune on-target properties.

[Treating specific childhood phobia in a single session? A systematic review of the literature]

OBJECTIVE

The essential feature of specific phobia is a persistent fear of clearly discernable, circumscribed objects or situations. The DSM-IV distinguishes four subtypes: animal, natural environment, blood-injection-injury, and situational. Specific phobias frequently co-occur. Specific phobia is one of the most common psychiatric disorders with a lifetime prevalence of 12.5% and is about twice as common in women as in men. Most phobias have a childhood onset except for the situational subtype which usually occurs during patients' twenties. It is well known that childhood anxiety increases the risk of psychiatric disorders such as depression and anxiety in later life, as well as the risk of suicide attempts and psychiatric hospitalization. Nonetheless, there are few studies on the psychobiology and pharmacotherapy of specific phobias. Neuroimaging studies have shown that specific phobia seems to be associated with amygdala (more specifically the right amygdala) and anterior cingulate cortex hyperactivation that is reduced after exposure therapy. The aim of this study is to propose the first systematic review of specific phobia treatment among children.

METHOD

The review follows the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) statement guidelines. Two databases (Medline and Web of Science) were searched combining the search terms: specific phobia and treatment. English and French language were imposed. There were no publication date or publication status limitations. Seventy-four studies met the inclusion criteria and 36 were included.

RESULTS

The goal of treatment is to achieve habituation and eventual extinction of the phobic reaction. Treatments for children's anxiety have been suggested to work through diverse processes such as counter-conditioning, extinction, habituation, change in catastrophic cognitions, development of coping skills, increased self-efficacy, emotional processing, and changes in expectancies and perceptions of dangerousness. Most phobias respond robustly to in vivo exposure, but this approach is associated with high dropout rates and low treatment acceptance. One Session Treatment, a variant of cognitive-behavioral therapy, combines graduated in vivo exposure, participant modeling, reinforcement, psychoeducation, cognitive challenges, and skills training in an intensive treatment model. The limited data available on medication shows little promise. Finally, relapse is a common phenomenon, and little is known on the long-term outcome of the illness.

D-cycloserine effects on extinction of conditioned responses to drug-related cues

D-cycloserine (DCS) is an N-methyl-D-aspartate (NMDA) receptor partial agonist that facilitates extinction of conditioned fear in animals and cue exposure therapy (CET) for fear and anxiety disorders in people. Recent preclinical and clinical studies have examined the effect of DCS on extinction of conditioned responses elicited by cues paired with administration of or withdrawal from drugs of abuse, including physiological responses, craving, withdrawal, and drug-seeking behavior. DCS facilitates extinction and blunts postextinction recovery of these responses in animal models, including place conditioning and drug self-administration, but DCS effects on CET in substance users/abusers are less robust. Some of the null effects in the clinical literature might be attributable to issues related to sample size, data characteristics, DCS administration, and participant characteristics, among others. In this review we describe the preclinical and clinical literatures on DCS modulation of extinction of addiction-related conditioned responses, consider possible limitations of the clinical studies that have been published to date, and propose ways of designing future clinical studies so as to maximize the probability of detecting a DCS effect. We also discuss concerns with regard to potential harmful effects of DCS-coupled CET in addicts and describe how these concerns might be mitigated. We conclude that it is as yet unclear whether DCS-coupled CET might be a useful approach in the treatment of addiction.

Excessive discounting of delayed reinforcers as a trans-disease process contributing to addiction and other disease-related vulnerabilities: emerging evidence

Delay discounting describes the devaluation of a reinforcer as a function of the delay until its receipt. Although all people discount delayed reinforcers, one consistent finding is that substance-dependent individuals tend to discount delayed reinforcers more rapidly than do healthy controls. Moreover, these higher-than-normal discounting rates have been observed in individuals with other behavioral maladies such as pathological gambling, poor health behavior, and overeating. This suggests that high rates of delay discounting may be a trans-disease process (i.e., a process that occurs across a range of disorders, making findings from one disorder relevant to other disorders). In this paper, we argue that delay discounting is a trans-disease process, undergirded by an imbalance between two competing neurobehavioral decision systems. Implications for our understanding of, and treatment for, this trans-disease process are discussed.

D-cycloserine facilitates extinction of cocaine self-administration in rats

Previous research has indicated that D-cycloserine [DCS; a N-methyl-D-aspartate (NMDA) partial agonist] facilitates the extinction of conditioned fear as well as the extinction of cocaine conditioned place preference. Sprague Dawley rats were first trained to self-administer cocaine and then we compared their extinction behavior (lever pressing) following treatment with vehicle; 15 mg/kg DCS; or 30 mg/kg DCS. We showed that 30 mg/kg DCS, but not 15 mg/kg significantly accelerated extinction of cocaine self-administration behavior when compared with saline by almost half (4 days vs. 9 days). At 2 weeks when all animals had extinguished, there were no longer differences between the groups. The present findings support of the potential of NMDA partial agonists as prospectively valuable in facilitating the extinction of cocaine-seeking behavior. More specifically, we demonstrate that 30 mg/kg DCS was effective at significantly accelerating the extinction of cocaine self-administration behavior in rats. These results provide further support for the potential of DCS as a treatment strategy for addiction.