Beneficial effects of the glutamate-modulating agent riluzole on disordered eating and pathological skin-picking behaviors

The neuropathology of Self-Injurious Behavior: Studies using animal models

Self-injurious behavior is a debilitating characteristic that is highly prevalent in autism and other neurodevelopmental disorders. In these populations, self-injury has typically been interpreted in relation to behavioral reinforcement and/or sensory stimulation. However, self-injury is also commonly exhibited by people with a variety of neuropsychiatric disorders, where it is typically described in relation to emotional regulation and the presence or absence of suicidal ideation. Interestingly, self-injury has also been documented in many non-human animal species, especially when exposed to early environmental deprivation, isolation, and distress. Despite the propensity of animals to self-injure under adverse conditions, animal models of self-injury have not been the focus of much research, and translation of the data from these models has largely been limited to autism and neurodevelopmental disorders. This review summarizes evidence that common biological and environmental mechanisms may contribute to vulnerability for self-injury in neurodevelopmental disorders, psychiatric disorders, and distressed animals, and that investigations using animal models may be highly beneficial when considering self-injury as a behavioral phenotype that exists across diagnostic categories. Investigations using animal models have revealed that individual differences in stress responses and anxiety-related behavior contribute to vulnerability for self-injury. Animal models have implicated dysregulation of monoaminergic, glutamatergic, and other neurotransmitter systems in expression of self-injury, and these models have suggested neural targets for pharmacotherapy that have potential relevance for diverse clinical populations.

Dermatillomania: Strategies for Developing Protective Biomaterials/Cloth

Dermatillomania or skin picking disorder (SPD) is a chronic, recurrent, and treatment resistant neuropsychiatric disorder with an underestimated prevalence that has a concerning negative impact on an individual’s health and quality of life. The current treatment strategies focus on behavioral and pharmacological therapies that are not very effective. Thus, the primary objective of this review is to provide an introduction to SPD and discuss its current treatment strategies as well as to propose biomaterial-based physical barrier strategies as a supporting or alternative treatment. To this end, searches were conducted within the PubMed database and Google Scholar, and the results obtained were organized and presented as per the following categories: prevalence, etiology, consequences, diagnostic criteria, and treatment strategies. Furthermore, special attention was provided to alternative treatment strategies and biomaterial-based physical treatment strategies. A total of six products with the potential to be applied as physical barrier strategies in supporting SPD treatment were shortlisted and discussed. The results indicated that SPD is a complex, underestimated, and underemphasized neuropsychiatric disorder that needs heightened attention, especially with regard to its treatment and care. Moreover, the high synergistic potential of biomaterials and nanosystems in this area remains to be explored. Certain strategies that are already being utilized for wound healing can also be further exploited, particularly as far as the prevention of infections is concerned.

The Pemoline Model of Self-Injurious Behavior: An Update

Neurodevelopmental disorders typically comprise a complex constellation of behavioral symptoms and neurochemical abnormalities. However, many of the symptoms are inconsistently expressed within any one particular patient group or overlap between patient groups. In other words, there is usually heterogeneity of symptoms between diagnostic groups, and there is often partial homogeneity of symptoms across these groups. These include cognitive deficits, emotional lability, and perseverative or aberrant behaviors. Animal models of neurodevelopmental disorders typically reproduce or mimic specific genetic, neurochemical, and/or behavioral sequelae, although they typically fail to replicate the entire spectrum of biological and behavioral characteristics. Indeed, it may be impractical or even impossible to model the entire spectrum of characteristics of a disorder in any single animal model. A focus on one or more specific behavioral characteristics that occur in multiple neurodevelopmental disorders (e.g., self-injury) may be a fruitful strategy. The development of these behaviorally focused models may yield increased understanding of the endogenous and environmental factors that confer vulnerability for aberrant behaviors that commonly occur in these disorders. One such behaviorally focused animal model is the pemoline model of self-injurious behavior.

Skin-Picking Disorder: A Guide to Diagnosis and Management

Skin-picking disorder, also known as excoriation disorder or psychogenic skin excoriations, is an obsessive-compulsive and related disorder that is classified with other body-focused repetitive-behavior disorders in the most recent edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5). Skin-picking disorder is associated with significant comorbidity and psychosocial dysfunction. The disorder has a female predominance across studies, and the average age of onset is variable but commonly in adolescence and adulthood. A full clinical and dermatologic examination and multidisciplinary approach is important in the diagnosis of this condition. There is no specific or recommended treatment option, but cognitive-behavioral therapy, particularly habit-reversal therapy and acceptance and commitment therapy have shown promise. Various pharmacological interventions have also been described to treat this condition in case reports and open and controlled trials. Specific classes of agents implemented include selective serotonin reuptake inhibitors (SSRIs), serotonin-norepinephrine reuptake inhibitors, antipsychotics, and glutaminergic-modulating agents. SSRIs and N-acetylcysteine have been shown to be the most effective of the pharmacological interventions.

Animal Models of Self-Injurious Behavior: An Update

Although self-injurious behavior is a common comorbid behavior problem among individuals with neurodevelopmental disorders, little is known about its etiology and underlying neurobiology. Interestingly, it shows up in various forms across patient groups with distinct genetic errors and diagnostic categories. This suggests that there may be shared neuropathology that confers vulnerability in these disparate groups. Convergent evidence from clinical pharmacotherapy, brain imaging studies, postmortem neurochemical analyses, and animal models indicates that dopaminergic insufficiency is a key contributing factor. This chapter provides an overview of studies in which animal models have been used to investigate the biochemical basis of self-injury and highlights the convergence in findings between these models and expression of self-injury in humans.

UPLC-MS/MS assay of riluzole in human plasma and cerebrospinal fluid (CSF): Application in samples from spinal cord injured patients

In the present study, a sensitive and robust LC-MS/MS method has been developed and validated for the quantification of riluzole in human plasma and cerebrospinal fluid (CSF) in clinical samples from patients with spinal cord injury (SCI). Riluzole and its labeled internal standard (IS) were isolated from plasma and CSF by liquid-liquid extraction using ethyl acetate. Riluzole (m/z 235→166) and IS (m/z 238→169) were detected by electrospray ionization (ESI) using multiple reaction monitoring (MRM) in a positive mode. The assay was linear in the concentration range of 0.5 (LLOQ, signal/noise ratio>10)-800ng/ml in plasma, and 1.0 (LLOQ)-800ng/ml in CSF samples. The intra- and inter-day accuracy in plasma were 94.2-110.0% and 97.8-102.0%, respectively, and those in CSF were 87.6-105.1% and 91.9-98.8%, respectively. The intra- and inter-day precision were 2.2-7.2% and 4.0-9.1%, respectively, in plasma, and 1.4-14.1% and 2.6-11.5%, respectively in CSF. Matrix effect was negligible from both matrices with signal percentages of 97.6-100.6% in plasma and 99.4-106.4% in CSF. The recoveries were >75% in plasma, >84% in CSF with low protein (53.9mg/dl), and >68% in CSF with high protein (348.2mg/dl). This method was successfully applied to quantify riluzole concentrations in plasma and CSF from patients with SCI.

Excoriation (skin-picking) disorder: a systematic review of treatment options

Although pathological skin-picking has been documented in the medical literature since the 19th century, it has only recently been included as a distinct entity in psychiatric classification systems. In the Diagnostic and Statistical Manual of Mental Disorders, 5th Edition and the proposed International Classification of Diseases, Eleventh Revision, excoriation (skin-picking) disorder (ED), also known as neurotic excoriation, psychogenic excoriation, or dermatillomania), is described as recurrent picking of skin, leading to skin lesions and significant distress or functional impairment. ED is listed as one of the obsessive-compulsive and related disorders, given its overlap with conditions such as trichotillomania (hair-pulling disorder). Arguably, its inclusion and delineation in the diagnostic nomenclature will lead to increased awareness of the condition, more research, and ultimately in treatment advances. This systematic review aims to provide readers with an up-to-date view of current treatment options for ED. A MEDLINE search of the ED treatment literature was conducted to collate relevant articles published between 1996 and 2017. The findings indicate that a number of randomized controlled trails on ED have now been published, and that current management options include behavioral therapy (habit reversal or acceptance-enhanced behavior therapy), and medication (selective serotonin reuptake inhibitors or N-acetyl cysteine).

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.

Pain and suicidality: insights from reward and addiction neuroscience

Suicidality is exceedingly prevalent in pain patients. Although the pathophysiology of this link remains unclear, it may be potentially related to the partial congruence of physical and emotional pain systems. The latter system's role in suicide is also conspicuous during setbacks and losses sustained in the context of social attachments. Here we propose a model based on the neural pathways mediating reward and anti-reward (i.e., allostatic adjustment to recurrent activation of the reward circuitry); both are relevant etiologic factors in pain, suicide and social attachments. A comprehensive literature search on neurobiology of pain and suicidality was performed. The collected articles were critically reviewed and relevant data were extracted and summarized within four key areas: (1) physical and emotional pain, (2) emotional pain and social attachments, (3) pain- and suicide-related alterations of the reward and anti-reward circuits as compared to addiction, which is the premier probe for dysfunction of these circuits and (4) mechanistically informed treatments of co-occurring pain and suicidality. Pain-, stress- and analgesic drugs-induced opponent and proponent states of the mesolimbic dopaminergic pathways may render reward and anti-reward systems vulnerable to sensitization, cross-sensitization and aberrant learning of contents and contexts associated with suicidal acts and behaviors. These findings suggest that pain patients exhibit alterations in the brain circuits mediating reward (depressed function) and anti-reward (sensitized function) that may affect their proclivity for suicide and support pain and suicidality classification among other "reward deficiency syndromes" and a new proposal for "enhanced anti-reward syndromes". We suggest that interventions aimed at restoring the balance between the reward and anti-reward networks in patients with chronic pain may help decreasing their suicide risk.

The role of NMDA receptors in human eating behavior: evidence from a case of anti-NMDA receptor encephalitis

Research in animal models has implicated N-methyl-D-aspartate (NMDA) receptors (NMDARs) in the control of food intake. Until now, these findings have been not replicated in humans. Here we describe a 22-year-old woman with anti-NMDAR encephalitis and no prior neurological or psychiatric history. Her clinical course was marked by successive eating disorders: anorexia followed by hyperphagia. We propose that, much as they do in other animals, NMDARs in humans interact with the neuroendocrine, homeostatic, and reward systems controlling food intake in the central and peripheral nervous system structures related to feeding and satiety.

The pemoline model of self-injurious behaviour

Traditional models of neuropsychiatric disorders consist of attempts to replicate the broad spectrum of behavioural and neurochemical sequelae that characterize a specific disorder. However, these disorders comprise complex constellations of symptoms, including emotional instability, perseverative thoughts, and aberrant behaviours. Close examination often reveals heterogeneity of symptom expression within patient groups and homogeneity in expression of specific symptoms across diagnostic categories. Accordingly, it may not be possible to model the entire spectrum of characteristics for any one of these disorders in any single animal model. A focus on one or more specific behavioural characteristics (e.g. self-injury) may be a more fruitful strategy. Development of behaviourally focused models yields increased understanding of the genetic basis and biochemical abnormalities that underlie specific psychiatric dysfunctions. Furthermore, by revealing pathophysiology that underlies specific disease characteristics, behaviourally focused models improve translational power and help to identify targets for effective pharmacotherapies. One such behaviourally focused animal model is the pemoline model of self-injurious behaviour.

Animal models of self-injurious behaviour: an overview

Self-injurious behaviour is highly prevalent in neurodevelopmental disorders. Interestingly, it is not restricted to any individual diagnostic group. Rather, it is exhibited in various forms across patient groups with distinct genetic defects and classifications of disorders. This suggests that there may be shared neuropathology that confers vulnerability. Convergent evidence from clinical pharmacotherapy, brain imaging studies, postmortem neurochemical analyses, and animal models indicates that dopaminergic insufficiency is a key culprit. This chapter provides an overview of studies in which animal models have been used to investigate the biochemical basis of self-injury, and highlights the convergence in findings between these models and expression of self-injury in humans.

Glutamate abnormalities in obsessive compulsive disorder: neurobiology, pathophysiology, and treatment

Obsessive compulsive disorder is prevalent, disabling, incompletely understood, and often resistant to current therapies. Established treatments consist of specialized cognitive-behavioral psychotherapy and pharmacotherapy with medications targeting serotonergic and dopaminergic neurotransmission. However, remission is rare, and more than a quarter of OCD sufferers receive little or no benefit from these approaches, even when they are optimally delivered. New insights into the disorder, and new treatment strategies, are urgently needed. Recent evidence suggests that the ubiquitous excitatory neurotransmitter glutamate is dysregulated in OCD, and that this dysregulation may contribute to the pathophysiology of the disorder. Here we review the current state of this evidence, including neuroimaging studies, genetics, neurochemical investigations, and insights from animal models. Finally, we review recent findings from small clinical trials of glutamate-modulating medications in treatment-refractory OCD. The precise role of glutamate dysregulation in OCD remains unclear, and we lack blinded, well-controlled studies demonstrating therapeutic benefit from glutamate-modulating agents. Nevertheless, the evidence supporting some important perturbation of glutamate in the disorder is increasingly strong. This new perspective on the pathophysiology of OCD, which complements the older focus on monoaminergic neurotransmission, constitutes an important focus of current research and a promising area for the ongoing development of new therapeutics.

Advances in pharmacotherapy for pediatric anxiety disorders

Pediatric anxiety disorders are prevalent, chronic, and often lead to significant impaired functioning that impacts both short- and long-term outcomes for children and adolescents. Treatment options include pharmacotherapy and psychosocial interventions. This presentation will review treatment advances specifically for pharmacotherapy. Current research supports serotonin reuptake inhibitors as the medication class to be the first-line treatment option for pediatric anxiety disorders. Available evidence for the efficacy of other classes of medications will be reviewed, along with the available approaches to manage partial responders and nonresponders. The risks and benefits of pharmacotherapy will also be reviewed. In addition, recent research has shown the potential promise of novel agents that act upon other neural systems implicated in the development of pediatric anxiety disorders. Novel compounds that affect the glutamate system will be discussed.

Review of the use of the glutamate antagonist riluzole in psychiatric disorders and a description of recent use in childhood obsessive-compulsive disorder

The antiglutamatergic drug riluzole (Rilutek) is presently being used off label in the treatment of psychiatric conditions in adult patients and, increasingly, in children. This article briefly reviews the pharmacology of this drug and its current investigative and clinical uses and adverse effects. It also reports on our experience to date in the study of the drug in children, with emphasis on adverse effects noted so far in these younger patients.

Maintenance electroconvulsive therapy in autistic catatonia: a case series review

The usage of electroconvulsive therapy for the acute resolution of catatonia in autistic children and adults is a novel area that has received increased attention over the past few years. Reported length of the acute ECT course varies among these patients, and there is no current literature on maintenance ECT in autism. The maintenance ECT courses of three patients with autism who developed catatonia are presented. Clinical, research, legal, and administrative implications for ECT treatment in this special population are discussed.

Electroconvulsive therapy in a man with autism experiencing severe depression, catatonia, and self-injury

We report the successful use of electroconvulsive therapy in a 19-year-old man with autism and mild mental retardation who developed severe depression with repeated suicide attempts, multiple symptoms of catatonia, and life-threatening repetitive self-injurious behaviors. After 3 years of failed psychotropic and behavioral interventions in inpatient settings, the patient demonstrated excellent remission of symptoms with bilateral electroconvulsive therapy.

Riluzole in the treatment of mood and anxiety disorders

Recent advances implicate amino acid neurotransmission in the pathophysiology and treatment of mood and anxiety disorders. Riluzole, which is approved and marketed for the treatment of amyotrophic lateral sclerosis, is thought to be neuroprotective through its modulation of glutamatergic neurotransmission. Riluzole has multiple molecular actions in vitro; the two that have been documented to occur at physiologically realistic drug concentrations and are therefore most likely to be clinically relevant are inhibition of certain voltage-gated sodium channels, which can lead to reduced neurotransmitter release, and enhanced astrocytic uptake of extracellular glutamate.Although double-blind, placebo-controlled trials are lacking, several open-label trials have suggested that riluzole, either as monotherapy or as augmentation of standard therapy, reduces symptoms of obsessive-compulsive disorder, unipolar and bipolar depression, and generalized anxiety disorder. In studies of psychiatrically ill patients conducted to date, the drug has been quite well tolerated; common adverse effects include nausea and sedation. Elevation of liver function tests is common and necessitates periodic monitoring, but has been without clinical consequence in studies conducted to date in psychiatric populations. Case reports suggest utility in other conditions, including trichotillomania and self-injurious behaviour associated with borderline personality disorder. Riluzole may hold promise for the treatment of several psychiatric conditions, possibly through its ability to modulate pathologically dysregulated glutamate levels, and merits further investigation.

Riluzole in psychiatry: a systematic review of the literature

BACKGROUND

The glutamate system seems to be an important contributor to the pathophysiology of mood and anxiety disorders. Thus, glutamatergic modulators are reasonable candidate drugs to test in patients with mood and anxiety disorders. Riluzole, a neuroprotective agent with anticonvulsant properties approved for the treatment of amyotrophic lateral sclerosis (ALS) is one such agent.

OBJECTIVE

To assess the potential risks and benefits of riluzole treatment in psychiatric patients.

METHODS

A PubMed search was performed using the keywords 'riluzole', 'inhibitor of glutamate release' and 'glutamatergic modulator' to identify all clinical studies and case reports involving riluzole in psychiatric patients.

RESULTS/CONCLUSION

Riluzole's side effect profile is favorable and preliminary results regarding riluzole for the treatment of severe mood, anxiety and impulsive disorders are encouraging.

Memantine in the treatment of binge eating disorder: an open-label, prospective trial

OBJECTIVE

To assess preliminarily the efficacy of memantine in binge eating disorder.

METHOD

This was an open-label, 12-week, flexible-dose (5-20 mg/day) trial of memantine in binge eating disorder. The primary outcome was frequency of binge days. Secondary outcomes included frequency of binge episodes, body-mass index (BMI), weight, Clinical Global Impressions Severity (CGI-S), Three Factor Eating Questionnaire (TFEQ), Montgomery-Asberg Depression Rating Scale (MADRS), Hamilton Anxiety Rating Scale (HAM-A), and Sheehan Disability Scale (SDS). Longitudinal random regression analysis was performed for frequency of binge days and episodes, BMI, weight, and CGI-S; analysis of baseline to endpoint change was performed for all outcomes.

RESULTS

Sixteen individuals received memantine; 15 completed at least one postbaseline evaluation, 9 completed the study. Mean dose at endpoint was 18.3 mg/day. Memantine was associated with significant reductions in frequency of binge days and episodes, severity of illness (p < .001 for both analyses), disinhibition on the TFEQ (p = .015), and disability on the SDS (p < .05 for three subscales). There was no significant change in BMI, weight, MADRS, HAM-A, and TFEQ cognitive restraint and hunger.

CONCLUSION

In this open-label trial, memantine was well tolerated and effective in reducing binge eating, severity of illness, and disability, but had little effect on BMI and weight.

Glutamatergic Synaptic Dysfunction and Obsessive-Compulsive Disorder

Obsessive-compulsive disorder (OCD) is a debilitating neuropsychiatric condition estimated to afflict 1-3% of the world population. The estimated financial impact in the treatment and management of OCD is in the billions of dollars annually in the US alone. At present there is a marked lack of evidence on the specific causes of OCD. Current hypotheses largely focus on the serotonin (5-HT) system on the basis of the effectiveness of selective serotonin reuptake inhibitors (SSRIs) in alleviating symptoms of patients with OCD, yet a considerable fraction of patients are non-responsive or minimally responsive to these agents. Despite this fact, SSRIs have remained the primary pharmacological treatment avenue for OCD. In recent years, multiple lines of evidence have implicated glutamatergic synaptic dysfunction within the cortico-striatal-thalamo-cortical (CSTC) brain circuit in the etiology of OCD and related disorders, thereby prompting intensified effort in the development and evaluation of agents that modulate glutamatergic neurotransmission for the treatment of OCD. With this in mind, here we review the following topics with respect to synaptic dysfunction and the neural circuitry underlying OCD: (1) evidence supporting the critical involvement of the CSTC circuit, (2) genetic studies supporting the involvement of glutamatergic dysfunction, (3) insights from genetic animal models of OCD, and (4) preliminary findings with glutamatergic neurotransmission-modulating agents in the treatment of OCD. Given the putative mechanistic overlap between OCD and the broader OC-spectrum of disorders, unraveling the synaptic basis of OCD has potential to translate into more effective treatments for an array of poorly understood human disorders.

Glutamate-mediated neuroplasticity in an animal model of self-injurious behaviour

Self-injurious behaviour (SIB) is exhibited by individuals with a broad variety of developmental disorders and genetic abnormalities, including autism and Lesch-Nyhan, Prader-Willi and Rett syndromes. Most research has focused on environmental factors that reinforce SIB, and less is known about the biological basis of this behaviour disorder. However, animal models have been developed to study the neurochemical pathology that underlies SIB. In one model, rats exhibit self-biting after repeated daily administration of moderately high doses of pemoline (100-200mg/kg). Dopaminergic and glutamatergic neurotransmission have been implicated in this model. Accordingly, we investigated the role of glutamatergic neurotransmission in pemoline-induced SIB, using the N-methyl-d-aspartate (NMDA) receptor antagonists MK-801 and memantine. MK-801 is a high affinity antagonist which blocks glutamate-mediated neuroplasticity and behavioural sensitization to other psychostimulants. It lessened the incidence of SIB, the time spent self-injuring, and the area of tissue damage in the pemoline model. Memantine, on the other hand, is a low affinity antagonist which does not disrupt glutamate-mediated neuroplasticity, and it had little if any effect on any measure of pemoline-induced SIB. These results suggest that repeated pemoline administration induces glutamate-mediated neuroplastic changes that lead to the eventual expression of SIB. Further investigation of these changes may reveal specific neurochemical factors that contribute to SIB in this animal model of self-injury.

An open-label trial of riluzole, a glutamate antagonist, in children with treatment-resistant obsessive-compulsive disorder

BACKGROUND

Obsessive-compulsive disorder (OCD) in childhood is often refractory to treatment. Riluzole, a glutamate antagonist, has theoretical support as an alternative pharmacological treatment and has demonstrated possible benefit in some open-label trials in adults with OCD.

METHODS

Six subjects, ages 8-16 years, were enrolled in a 12-week open-label trial of riluzole for OCD symptoms that had resisted prior treatments. OCD symptoms and adverse effects of drug were monitored.

RESULTS

Four of 6 subjects had clear benefit, with reduction of more than 46% (39% overall) on Children's Yale-Brown Obsessive-Compulsive Scale, and "Much Improved" or "Very Much Improved" on the Clinical Global Impressions-Improvement scale. Two subjects had no clinically meaningful change in symptom severity by 12 weeks, but 1 subject improved thereafter. There were no adverse effects of drug sufficient to cause discontinuation or reduction of dose. All subjects elected to continue riluzole after the 12-week trial.

CONCLUSIONS

Riluzole may be beneficial for treatment-resistant OCD in young subjects and seems well tolerated. A placebo-controlled trial of the drug is planned.