Ketamine induces immediate and delayed alterations of OCD-like behavior

Ketamine Infusion in a Resistant Obsessive-Compulsive Disorder Patient in Bangladesh with Severe Suicidal Ideation: A Case Report

Treatment of resistant obsessive-compulsive disorder (OCD) typically results in insufficient symptom alleviation, and even long-term medication often fails to have the intended effect. Ketamine is a potent non-competitive antagonist of the N-methyl-D-aspartate (NMDA) receptor. Studies have shown that low-dose ketamine infusion results in a considerable reduction in obsessive-compulsive symptoms and a rapid resolution of suicidal ideation. This is a case report on the effect of intravenous ketamine infusion on a patient with resistant OCD and severe suicidal ideation. Intravenous (IV) ketamine was given once a week over consecutive three weeks with necessary precautions. Psychometric tools such as the Yale-Brown Obsessive Compulsive Scale (Y-BOCS), the Clinical Global Impressions Scale (CGI-S), the Beck Scale for Suicidal Ideations (BSSI), and Depression Anxiety and Stress Scale 21 (DASS-21) were applied before and after infusions. Obsessive-compulsive symptoms and suicidal severity started to decrease rapidly after the first infusion. However, after a transient improvement, these symptoms again began to increase after a stressful incident on the second day of the first infusion. All the symptoms measured by validated rating scales showed continued improvement after the following two infusions. The improvement was sustained until discharge (one week after the last infusion) and subsequent follow-up in the sixth and 12th weeks. The role of ketamine in reducing suicidal thoughts and behavior is already established. Very few studies emphasized its effectiveness in improving severe/resistant obsessive-compulsive symptoms. This pioneering work may offer scope for similar research in the relevant field.

Establishing an OCD Model in BALB/c Mice Using RU24969: A Molecular and Behavioural Study of Optimal Dose Selection

Obsessive-compulsive disorder (OCD) is a disabling disease characterized by distressing obsessions and repetitive compulsions. The etiology of OCD is poorly known, and mouse modeling allows to clarify the genetic and neurochemical basis of this disorder and to investigate potential treatments. This study evaluates the impact of the 5-HT1B agonist RU24969 on the induction of OCD-like behaviours in female BALB/c mice (n = 30), distributed across five groups receiving varying doses of RU24969. Behavioural assessments, including marble test, tail suspension test, sucrose preference test, forced swim test, and nestlet shredding test, were conducted. Gene expression and protein quantitation of Gabra1 and serotonin transporter in mouse brain were also performed. Marble-burying behaviour increased significantly at high doses of RU24969 (15-20 mg/kg). The forced swimming test consistently showed elevated values at the same high concentrations, compared to the control. Altered reward-seeking behaviour was indicated by the sucrose preference test, notably at 15 and 20 mg/kg doses of RU24969. Nestlet shredding results did not show statistical significance among the tested animal groups. Gene expression analysis revealed reduced Gabra1 expression with increasing doses of RU, while serotonin transporter was not related to varying doses of RU24969. Western blotting corroborated these trends. The results underscore complex interactions between the serotonin system, GABAergic signaling, and OCD-relevant behaviours and suggest the use of intraperitoneal injection of 15 mg/kg of RU24969 to induce OCD-like behaviour in BALB/c mouse models.

Serotonergic agonism and pharmacologically-induced adolescent stress cause operant-based learning deficits in mice

BACKGROUND

The interplay between environmental stress and genetic factors is thought to play an important role in the pathogenesis and maintenance of obsessive-compulsive disorder (OCD). However, the relative contribution of these causative antecedents in the manifestation of cognitive inflexibility-a phenotype often seen in obsessive-compulsive (OC)- spectrum disorders-is not fully understood.

METHOD

In this study, we treated mice with 50 mg/L corticosterone (CORT, a glucocorticoid stress hormone) in their drinking water during adolescence. In adulthood, we assessed anxiety-like behaviour and locomotor activity; along with operant-based discrimination and reversal learning. RU-24969, a selective serotonin receptor 5-HT1A/1B receptor agonist, was used as an acute pharmacological model of OC-like behaviour. RU-24969 (5 mg/kg) was administered prior to each reversal learning testing session.

RESULTS

We found that acute treatment with 5 mg/kg RU-24969 induced stereotyped hyperlocomotion in vehicle- and CORT-treated mice. Furthermore, pre-treatment with CORT in adolescence produced subtle anxiety-like behaviour in adult mice, and also resulted in an impairment to late-stage discrimination learning and alterations to reversal learning. Finally, acute treatment with 5 mg/kg RU-24969 caused an impairment to early-stage reversal learning.

CONCLUSION

Whilst we revealed dissociable detrimental effects of adolescent CORT treatment and acute 5-HT1A/1B receptor agonism on discrimination and reversal learning, respectively, we did not find evidence of additive deleterious effects of these two treatments. We therefore suggest that while disrupted serotonergic signalling is likely to be involved in the cognitive phenotype of OC-spectrum disorders, distinct neuropathological pathways may be at play in mediating the role of stress as an antecedent in OCD and related illnesses.

Mechanisms of pathogenesis and environmental moderators in preclinical models of compulsive-like behaviours

Obsessive-compulsive and related disorders (OCRD) is an emergent class of psychiatric illnesses that contributes substantially to the global mental health disease burden. In particular, the prototypical illness, obsessive-compulsive disorder (OCD), has a profoundly deleterious effect on the quality of life of those with lived experience. Both clinical and preclinical studies have investigated the genetic and environmental influences contributing to the pathogenesis of obsessive-compulsive and related disorders. Significant progress has been made in recent years in our understanding of the genetics of OCD, along with the critical role of common environmental triggers (e.g., stress). Some of this progress can be attributed to the sophistication of rodent models used in the field, particularly genetic mutant models, which demonstrate promising construct, face, and predictive validity. However, there is a paucity of studies investigating how these genetic and environmental influences interact to precipitate the behavioural, cellular, and molecular changes that occur in OCD. In this review, we assert that preclinical studies offer a unique opportunity to carefully manipulate environmental and genetic factors, and in turn to interrogate gene-environment interactions and relevant downstream sequelae. Such studies may serve to provide a mechanistic framework to build our understanding of the pathogenesis of complex neuropsychiatric disorders such as OCD. Furthermore, understanding gene-environment interactions and pathogenic mechanisms will facilitate precision medicine and other future approaches to enhance treatment, reduce side-effects of therapeutic interventions, and improve the lives of those suffering from these devastating disorders.

[Combination of ketamine and esketamine with Exposure and Response Prevention (ERP) therapy for Obsessive-Compulsive Disorder]

Obsessive-Compulsive Disorder (OCD), characterized by the combination of obsession and compulsion, is a clinical and therapeutic challenge. Many patients with OCD do not respond to first-line treatments such as serotonin selective reuptake inhibitors (SSRIs) and exposure and response prevention psychotherapy (ERP). For these resistant patients, some preliminary studies have shown that ketamine, a non-selective glutamatergic NMDA receptors antagonist, could improve the obsessive symptoms. A number of these studies have also suggested that the combination of ketamine with ERP psychotherapy may jointly potentiate the effectiveness of ketamine and ERP. In this paper, we present the existing data on the combined use of ketamine with ERP psychotherapy for OCD. We suggest that modulation of NMDA receptor activity and glutamatergic signaling by ketamine may promote the therapeutic mechanisms involved in ERP such as fear extinction and brain plasticity mechanisms. Finally, we propose a ketamine-augmented ERP psychotherapy (KAP-ERP) protocol in OCD, and we present the limitations associated with its application in clinical practice.

Clinical Effectiveness of N-Methyl-D-Aspartate (NMDA) Receptor Antagonists in Adult Obsessive-Compulsive Disorder (OCD) Treatment: A Systematic Review

Obsessive-compulsive disorder (OCD) is a neuropsychiatric disorder that affects approximately 2% of the human population. Traditional treatment of OCD includes selective serotonin reuptake inhibitor (SSRI) or serotonin reuptake inhibitor (SRI) treatment along with cognitive behavioral therapy (CBT). Nearly 25%-30% of OCD patients do not respond to SSRIs. Glutamatergic agents are currently being studied for the treatment of OCD due to the glutamatergic pathway in the brain, related to OCD, and the role of the cortico-striato-thalamic circuit (CSTC). This review assesses the clinical effectiveness of N-methyl-D-aspartate (NMDA) antagonists, ketamine/esketamine, memantine, and amantadine, for adult patients with OCD. Inclusion criteria include human studies published within the last 15 years, with patients diagnosed with OCD, aged over 18 years, with only psychiatric comorbidities, and full-text articles. Papers that included interventions other than CBT, exposure with response prevention (ERP), and SSRI/SRI were excluded. Articles were searched for using PubMed, PubMed Central, Medical Literature Analysis and Retrieval System Online, GeorgiA LIbrary LEarning Online, EBSCO Information Services, OpenAthens, Multidisciplinary Digital Publishing Institute, and Google Scholar databases, last searched on December 2, 2022. The risk of bias was assessed using Cochrane Risk of Bias tools, the Scale for the Assessment of Narrative Review Articles (SANRA) checklist for literature reviews, and the Joanna Briggs Institute (JBI) Critical Appraisal Checklist for quasi-experimental studies. Results were presented and synthesized by Excel spreadsheet analysis. The database search yielded 4,221 articles, which was cut down to 18 articles by inclusion/exclusion criteria, including duplications. 80% of the ketamine studies resulted in a significant reduction of obsessions and compulsions based on the Yale-Brown Obsessive-Compulsive Scale (Y-BOCS), and each of the memantine and amantadine studies displayed clinical effectiveness, also. Limitations include the small number of amantadine studies and the limited availability of other NMDA receptor (NMDAR) antagonist-focused studies. This systematic review shows that ketamine is an effective drug for the treatment of non-refractory, mild to moderate OCD, and memantine and amantadine are effective augmentation agents for the treatment of mild to severe OCD.

Prophylactic (R,S)-Ketamine Is Effective Against Stress-Induced Behaviors in Adolescent but Not Aged Mice

BACKGROUND

(R,S)-ketamine, an N-methyl-D-aspartate receptor antagonist, is frequently used as an anesthetic and as a rapid-acting antidepressant. We and others have reported that (R,S)-ketamine is prophylactic against stress in adult mice but have yet to test its efficacy in adolescent or aged populations.

METHODS

Here, we administered saline or (R,S)-ketamine as a prophylactic at varying doses to adolescent (5-week-old) and aged (24-month-old) 129S6/SvEv mice of both sexes 1 week before a 3-shock contextual fear-conditioning (CFC) stressor. Following CFC, we assessed behavioral despair, avoidance, perseverative behavior, locomotion, and contextual fear discrimination. To assess whether the prophylactic effect could persist into adulthood, adolescent mice were injected with saline or varying doses of (R,S)-ketamine and administered a 3-shock CFC as a stressor 1 month later. Mice were then re-exposed to the aversive context 5 days later and administered behavioral tests as aforementioned. Brains were also processed to quantify Cyclooxygenase 2 expression as a proxy for inflammation to determine whether the prophylactic effects of (R,S)-ketamine were partially due to changes in brain inflammation.

RESULTS

Our data indicate that (R,S)-ketamine is prophylactic at sex-specific doses in adolescent but not aged mice. (R,S)-ketamine attenuated learned fear and perseverative behavior in females, reduced behavioral despair in males, and facilitated contextual fear discrimination in both sexes. (R,S)-ketamine reduced Cyclooxygenase 2 expression specifically in ventral Cornu Ammonis region 3 of male mice.

CONCLUSIONS

These findings demonstrate that prophylactic (R,S)-ketamine efficacy is sex, dose, and age dependent and will inform future studies investigating (R,S)-ketamine efficacy across the lifespan.

Ketamine increases activity of a fronto-striatal projection that regulates compulsive behavior in SAPAP3 knockout mice

Obsessive-Compulsive Disorder (OCD), characterized by intrusive thoughts (obsessions) and repetitive behaviors (compulsions), is associated with dysfunction in fronto-striatal circuits. There are currently no fast-acting pharmacological treatments for OCD. However, recent clinical studies demonstrated that an intravenous infusion of ketamine rapidly reduces OCD symptoms. To probe mechanisms underlying ketamine’s therapeutic effect on OCD-like behaviors, we used the SAPAP3 knockout (KO) mouse model of compulsive grooming. Here we recapitulate the fast-acting therapeutic effect of ketamine on compulsive behavior, and show that ketamine increases activity of dorsomedial prefrontal neurons projecting to the dorsomedial striatum in KO mice. Optogenetically mimicking this increase in fronto-striatal activity reduced compulsive grooming behavior in KO mice. Conversely, inhibiting this circuit in wild-type mice increased grooming. Finally, we demonstrate that ketamine blocks the exacerbation of grooming in KO mice caused by optogenetically inhibiting fronto-striatal activity. These studies demonstrate that ketamine increases activity in a fronto-striatal circuit that causally controls compulsive grooming behavior, suggesting this circuit may be important for ketamine’s therapeutic effects in OCD.

Intravenous infusion of ketamine rapidly reduces obsessive-compulsive disorder symptoms. Here, the authors show in mice that ketamine acts by increasing activity in a fronto-striatal circuit that causally controls compulsive grooming behaviour.

Therapeutic Potentials of Ketamine and Esketamine in Obsessive-Compulsive Disorder (OCD), Substance Use Disorders (SUD) and Eating Disorders (ED): A Review of the Current Literature

The obsessive–compulsive spectrum refers to disorders drawn from several diagnostic categories that share core features related to obsessive–compulsive disorder (OCD), such as obsessive thoughts, compulsive behaviors and anxiety. Disorders that include these features can be grouped according to the focus of the symptoms, e.g., bodily preoccupation (i.e., eating disorders, ED) or impulse control (i.e., substance use disorders, SUD), and they exhibit intriguing similarities in phenomenology, etiology, pathophysiology, patient characteristics and clinical outcomes. The non-competitive N-methyl-D-aspartate receptor (NMDAr) antagonist ketamine has been indicated to produce remarkable results in patients with treatment-resistant depression, post-traumatic stress disorder and OCD in dozens of small studies accrued over the past decade, and it appears to be promising in the treatment of SUD and ED. However, despite many small studies, solid evidence for the benefits of its use in the treatment of OCD spectrum and addiction is still lacking. Thus, the aim of this perspective article is to examine the potential for ketamine and esketamine in treating OCD, ED and SUD, which all involve recurring and intrusive thoughts and generate associated compulsive behavior. A comprehensive and updated overview of the literature regarding the pharmacological mechanisms of action of both ketamine and esketamine, as well as their therapeutic advantages over current treatments, are provided in this paper. An electronic search was performed, including all papers published up to April 2021, using the following keywords (“ketamine” or “esketamine”) AND (“obsessive” OR “compulsive” OR “OCD” OR “SUD” OR “substance use disorder” OR “addiction” OR “craving” OR “eating” OR “anorexia”) NOT review NOT animal NOT “in vitro”, on the PubMed, Cochrane Library and Web of Science online databases. The review was conducted in accordance with preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines. The use and efficacy of ketamine in SUD, ED and OCD is supported by glutamatergic neurotransmission dysregulation, which plays an important role in these conditions. Ketamine’s use is increasing, and preliminary data are optimistic. Further studies are needed in order to better clarify the many unknowns related to the use of both ketamine and esketamine in SUD, ED and OCD, and to understand their long-term effectiveness.

Methoxphenidine (MXP) induced abnormalities: Addictive and schizophrenia-related behaviours based on an imbalance of neurochemicals in the brain

BACKGROUND AND PURPOSE

Methoxphenidine is a dissociative-based novel psychoactive designer drug. Although fatal accidents from methoxphenidine abuse have been reported, recreational use of the drug continues. We aim to provide scientific supportfor legal regulation of recreational abuse of methoxphenidine by demonstrating its the pharmacological action.

EXPERIMENTAL APPROACH

Addictive potential of methoxphenidine was examined using intravenous self-administration test with rats and conditioned place preference test with mice. Further, a series of behavioural tests (open field test, elevated plus maze test, novel object recognition test, social interaction test and tail suspension test) performed to assess whether methoxphenidine caused schizophrenia-related symptoms in mice. Additionally, neurotransmitter enzyme-linked immunosorbent assay and western blot were used to confirm methoxphenidine-induced neurochemical changes in specific brain regions related to abnormal behaviours.

KEY RESULTS

Methoxphenidine caused addictive behaviours via reinforcing and rewarding effects. Consistently, methoxphenidine induced over-activation of dopamine pathways in the nuclear accumbens, indicating activation of the brain reward circuit. Also, methoxphenidine caused all categories of schizophrenia-related symptoms, including positive symptoms (hyperactivity, impulsivity), negative symptoms (anxiety, social withdrawal, depression) and cognitive impairment. Consistently, methoxphenidine led to the disruption of the hippocampal-prefrontal cortex pathway that is considered to be pathological involved in schizophrenia.

CONCLUSIONS AND IMPLICATIONS

We demonastrate that methoxphenidine causes addictive and schizophrenia-like behaviours and induces neurochemical changes in brain regions associated with these behaviours. We propose that methoxphenidine could be used in developing useful animal disease models and that it also requires legal restrictions on its recreational use.

Increased Compulsivity in Adulthood after Early Adolescence Immune Activation: Preclinical Evidence

Immune activation during early developmental stages has been proposed as a contributing factor in the pathogenesis of neuropsychiatric conditions such as obsessive-compulsive disorder, attention-deficit/hyperactivity disorder, and autism in both human and animal studies. However, its relationship with the vulnerability to inhibitory control deficit, which is a shared feature among those conditions, remains unclear. The present work studied whether postnatal immune activation during early adolescence, combined with exposure to early-life adverse events, could lead to adult vulnerability to impulsive and/or compulsive behaviors. Male Wistar rats were exposed to lipopolysaccharide (LPS) in early adolescence at postnatal day 26 (PND26). During peripuberal period, half of the animals were exposed to a mild stress protocol. In adulthood, behavioral assessment was performed with the aid of the sustained attentional 5-choice serial reaction time (5-CSRT) task, schedule-induced polydipsia (SIP), and open-field locomotor activity and novelty reactivity. Rats exposed to LPS showed more compulsive responses than their control counterparts on 5-CSRT task, although no differences were observed in SIP or locomotor responses. Our study contributes to the knowledge of the relationship between immune activation and inhibitory control deficit. Future studies should aim to disentangle how, and to what extent, immune activation impacts behavior, and to understand the role of early life mild stress.

Serotonin 5-HT1B receptor-mediated behavior and binding in mice with the overactive and dysregulated serotonin transporter Ala56 variant

RATIONALE

Elevated whole-blood serotonin (5-HT) is a robust biomarker in ~ 30% of patients with autism spectrum disorders, in which repetitive behavior is a core symptom. Furthermore, elevated whole-blood 5-HT has also been described in patients with pediatric obsessive-compulsive disorder. The 5-HT_1B receptor is associated with repetitive behaviors seen in both disorders. Chronic blockade of serotonin transporter (SERT) reduces 5-HT_1B receptor levels in the orbitofrontal cortex (OFC) and attenuates the sensorimotor deficits and hyperactivity seen with the 5-HT_1B agonist RU24969. We hypothesized that enhanced SERT function would increase 5-HT_1B receptor levels in OFC and enhance sensorimotor deficits and hyperactivity induced by RU24969.

OBJECTIVES

We examined the impact of the SERT Ala56 mutation, which leads to enhanced SERT function, on 5-HT_1B receptor binding and 5-HT_1B-mediated sensorimotor deficits.

METHODS

Specific binding to 5-HT_1B receptors was measured in OFC and striatum of naïve SERT Ala56 or wild-type mice. The impact of the 5-HT_1A/1B receptor agonist RU24969 on prepulse inhibition (PPI) of startle, hyperactivity, and expression of cFos was examined.

RESULTS

While enhanced SERT function increased 5-HT_1B receptor levels in OFC of Ala56 mice, RU24969-induced PPI deficits and hyperlocomotion were not different between genotypes. Baseline levels of cFos expression were not different between groups. RU24969 increased cFos expression in OFC of wild-types and decreased cFos in the striatum.

CONCLUSIONS

While reducing 5-HT_1B receptors may attenuate sensorimotor gating deficits, increased 5-HT_1B levels in SERT Ala56 mice do not necessarily exacerbate these deficits, potentially due to compensations during neural circuit development in this model system.

Determinants of Schizophrenia Endophenotypes Based on Neuroimaging and Biochemical Parameters

Despite extensive research, there is no convincing evidence of a reliable diagnostic biomarker for schizophrenia beyond clinical observation. Disorders of glutamatergic neurotransmission associated with N-methyl-D-aspartate (NMDA) receptor insufficiency, neuroinflammation, and redox dysregulation are the principal common mechanism linking changes in the periphery with the brain, ultimately contributing to the emergence of negative symptoms of schizophrenia that underlie differential diagnosis. The aim of the study was to evaluate the influence of these systems via peripheral and cerebral biochemical indices in relation to the patient's clinical condition. Using neuroimaging diagnostics, we were able to define endophenotypes of schizophrenia based on objective laboratory data that form the basis of a personalized approach to diagnosis and treatment. The two distinguished endophenotypes differed in terms of the quality of life, specific schizophrenia symptoms, and glutamatergic neurotransmission metabolites in the anterior cingulate gyrus. Our results, as well as further studies of the excitatory or inhibitory balance of microcircuits, relating the redox systems on the periphery with the distant regions of the brain might allow for predicting potential biomarkers of neuropsychiatric diseases, including schizophrenia. To the best of our knowledge, our study is the first to identify an objective molecular biomarker of schizophrenia outcome.