Synergistic psychedelic - NMDAR modulator treatment for neuropsychiatric disorders.

Modern research data suggest a therapeutic role for serotonergic psychedelics in depression and other neuropsychiatric disorders, although psychotomimetic effects may limit their widespread utilization. Serotonergic psychedelics enhance neuroplasticity via serotonin 2 A receptors (5HT2AR) activation and complex serotonergic-glutamatergic interactions involving the ionotropic glutamate receptors, tropomyosin receptor kinase B (TrkB) and the mammalian target of rapamycin (mTOR). N-methyl-d-aspartate receptors (NMDAR) channel antagonists, i.e. ketamine, and glycine modulatory site full and partial agonists, i.e., D-serine (DSR) and D-cycloserine (DCS), share some of these mechanisms of action and have neuroplastic and antidepressant effects. Moreover, procognitive effects have been reported for DSR and DCS and 5HT2AR-NMDAR interactions modulate neuronal excitability in prefrontal cortex and represent a target for new antipsychotics. We hypothesize that the synchronous administration of a psychedelic and a NMDAR modulator may increase the therapeutic impact of each of the treatment components and allow for dose adjustments and improved safety. We propose to initially focus research on the acute concurrent administration of psilocybin and DSR or DCS in depression.

Could psychedelic drugs have a role in the treatment of schizophrenia? Rationale and strategy for safe implementation.

Schizophrenia is a widespread psychiatric disorder that affects 0.5-1.0% of the world's population and induces significant, long-term disability that exacts high personal and societal cost. Negative symptoms, which respond poorly to available antipsychotic drugs, are the primary cause of this disability. Association of negative symptoms with cortical atrophy and cell loss is widely reported. Psychedelic drugs are undergoing a significant renaissance in psychiatric disorders with efficacy reported in several conditions including depression, in individuals facing terminal cancer, posttraumatic stress disorder, and addiction. There is considerable evidence from preclinical studies and some support from human studies that psychedelics enhance neuroplasticity. In this Perspective, we consider the possibility that psychedelic drugs could have a role in treating cortical atrophy and cell loss in schizophrenia, and ameliorating the negative symptoms associated with these pathological manifestations. The foremost concern in treating schizophrenia patients with psychedelic drugs is induction or exacerbation of psychosis. We consider several strategies that could be implemented to mitigate the danger of psychotogenic effects and allow treatment of schizophrenia patients with psychedelics to be implemented. These include use of non-hallucinogenic derivatives, which are currently the focus of intense study, implementation of sub-psychedelic or microdosing, harnessing of entourage effects in extracts of psychedelic mushrooms, and blocking 5-HT2A receptor-mediated hallucinogenic effects. Preclinical studies that employ appropriate animal models are a prerequisite and clinical studies will need to be carefully designed on the basis of preclinical and translational data. Careful research in this area could significantly impact the treatment of one of the most severe and socially debilitating psychiatric disorders and open an exciting new frontier in psychopharmacology.

D-aspartate oxidase gene duplication induces social recognition memory deficit in mice and intellectual disabilities in humans.

The D-aspartate oxidase (DDO) gene encodes the enzyme responsible for the catabolism of D-aspartate, an atypical amino acid enriched in the mammalian brain and acting as an endogenous NMDA receptor agonist. Considering the key role of NMDA receptors in neurodevelopmental disorders, recent findings suggest a link between D-aspartate dysmetabolism and schizophrenia. To clarify the role of D-aspartate on brain development and functioning, we used a mouse model with constitutive Ddo overexpression and D-aspartate depletion. In these mice, we found reduced number of BrdU-positive dorsal pallium neurons during corticogenesis, and decreased cortical and striatal gray matter volume at adulthood. Brain abnormalities were associated with social recognition memory deficit at juvenile phase, suggesting that early D-aspartate occurrence influences neurodevelopmental related phenotypes. We corroborated this hypothesis by reporting the first clinical case of a young patient with severe intellectual disability, thought disorders and autism spectrum disorder symptomatology, harboring a duplication of a chromosome 6 region, including the entire DDO gene.

Behavioral and cognitive effects of the N-methyl-D-aspartate receptor co-agonist D-serine in healthy humans: initial findings.

The efficacy of compounds having agonistic activity at the glycine site associated with the N-methyl-D-aspartate receptor (NMDAR) is presently assessed in psychiatric disorders. In contrast to NMDAR antagonists, the neuropsychiatric effects of NMDAR agonists in the healthy human organism are not known. We studied neuropsychiatric and neurochemical effects of the NMDAR-glycine site obligatory co-agonist d-serine (DSR) in healthy subjects using a randomized, controlled crossover challenge design including a baseline assessment day and two DSR/placebo administration days. Thirty-five subjects aged 23-29 years participated in the study and received a 2.1 g orally administered DSR dose. The main outcome measures were the changes in scores of mood-related Visual Analogue Scale (VAS), Continuous Performance Test-Identical Pairs (CPT-IP), and Rey Auditory Verbal Learning Test (RAVLT). DSR acute administration: (1) was well tolerated and resulted at 2 h in ≥ 200 times increase in DSR serum levels; (2) elicited reduced VAS-measured depression and anxiety feelings; (3) improved attention and vigilance as measured by CPT-IP D-prime score; (4) preferentially improved performance in RAVLT list 7 reflecting ability to retain information over interference; (5) had significant but nonspecific effects on Category Fluency and Benton Visual Retention tests; and (6) did not affect glycine and glutamate serum levels. These data indicate that in healthy subjects, DSR reduces subjective feelings of sadness and anxiety and has procognitive effects that are overall opposed to the known effects of NMDAR antagonists. The findings are relevant to translational research of NMDAR function and the development of NMDAR-glycine site treatments for specific psychiatric entities. ClinicalTrials.gov: Behavioral and Cognitive Effects of the N-methyl-D-aspartate Receptor (NMDAR) Co-agonist D-serine in Healthy Humans; http://www.clinicaltrials.gov/ct2/show/NCT02051426?term=NCT02051426&rank=1; NCT02051426.

Autoimmune-induced glutamatergic receptor dysfunctions: conceptual and psychiatric practice implications.

Glutamatergic neurotransmission is mediated via complex receptorial systems including N-methyl-d-aspartate (NMDA), alpha-amino-3-hydroxy-5-methyl-4-isoxazolpropionic acid (AMPA) and metabotropic receptor subtypes and plays a critical role in the modulation of synaptic plasticity, mood, cognitive processes and motor behavior. Glutamatergic function deficits are hypothesized to contribute to the pathogenesis of neuropsychiatric disorders, including schizophrenia, mood and movement disorders. Accumulating data are rapidly leading to the characterization of specific types of autoimmune encephalitis in which the receptors and proteins critically involved in glutamatergic neurotransmission, e.g., NMDA, AMPA receptors, are antigen targets. Characteristic of these syndromes, antibodies alter the structure and/or function of the corresponding neuronal antigen resulting in clinical pictures that resemble pharmacological disease models. Presently the best characterized autoimmune glutamatergic disorder is anti-NMDA receptor encephalitis. This disorder manifests with intertwined psychiatric and neurological features, defines a new syndrome, reclassifies poorly defined clinical states and extends previous hypotheses, such as hypo-NMDA receptor function in schizophrenia. The characterization of autoimmune-induced glutamatergic receptor dysfunctions (AGRD) is likely to have a substantial conceptual impact upon our understanding of neuropsychiatric disorders including schizophrenia, affective and movement dysfunctions. Further definition of AGRD will provide additional guidelines for psychiatric diagnoses, identification of homogeneous patient subtypes within broad phenomenological classifications and will contribute to the development of personalized treatments. The body of knowledge already accumulated on anti-NMDA receptor encephalitis highlights the need for wide dissemination of these concepts among psychiatrists, and in suspected cases, for early recognition, prompt clinical and laboratory investigation and efficient interface between mental health and medical teams.

Hypnotizability is associated with a protective but not acquisitive self-presentation style.

Self-presentation refers to the behavioral strategies a person adopts to convey desired social images of oneself to other people. The Concern for Appropriateness Scale (CAS) measures a defensive and fearful social approach aimed at avoiding social threats whereas the Revised Self-Monitoring Scale (RSMS) measures an active and flexible social approach aimed at gaining power and status. In this study, a significant correlation was found between hypnotizability, as measured by the Stanford Hypnotic Susceptibility Scale, Form C (SHSS:C) scores and CAS (r = .43, p = .002) but not between hypnotizability and RSMS (r = .070, p = .631). These results suggest that a protective self-presentation style may incline certain individuals to cooperate with hypnotic suggestions.

Glycine site agonists of the N-methyl-D-aspartate receptor and Parkinson's disease: a hypothesis.

Limitations of current pharmacological approaches to Parkinson's disease (PD) highlight the need for the development of nondopaminergic therapeutic strategies. The potential role of glutamatergic neurotransmission modulators, including those active at the N-methyl-D-aspartate receptor (NMDAR), is presently under investigation. Most literature proposes the use of NMDAR antagonists based on neurodegenerative theories of NMDAR function. Nevertheless, NMDAR antagonism has proven disappointing in clinical trials and may be associated with serious adverse events. More recent theories indicate that NMDAR target selectivity may be a cardinal prerequisite for efficacy, with present efforts being devoted primarily to development of NMDAR-NR2B subunit antagonists. We propose a novel hypothesis according to which NMDAR stimulation, accomplished through allosteric modulation via the glycine modulatory site, may be beneficial in late-phase PD. This hypothesis stems from: (1) meta-analysis of randomized controlled trials performed in schizophrenia, indicating that glycine site agonists (eg, glycine, D-serine) alleviate antipsychotic-induced parkinsonian symptoms; (2) clinical observations indicating that NMDAR hypofunction is associated with motor disturbances; (3) results of a preliminary D-serine trial in PD; (4) data indicating glycine efficacy in a rat tardive dyskinesia model; and (5) no evidence of excitotoxic damage following chronic high-dose glycine nutritional supplementation. This hypothesis is discussed in the context of glycine site agonist effects on intrasynaptic NMDAR subunits and striatal synaptic plasticity.

A randomized add-on trial of high-dose D-cycloserine for treatment-resistant depression.

Antagonism of N-methyl-D-aspartate glutamatergic receptors (NMDAR) may represent an effective antidepressant mechanism. D-cycloserine (DCS) is a partial agonist at the NMDAR-associated glycine modulatory site that at high doses acts as a functional NMDAR antagonist. Twenty-six treatment-resistant major depressive disorder patients participated in a double blind, placebo-controlled, 6-wk parallel group trial with a gradually titrated high dose (1000 mg/d) of DCS added to their antidepressant medication. DCS treatment was well tolerated, had no psychotomimetic effects and led to improvement in depression symptoms as measured by Hamilton Depression Rating Scale (HAMD; p = 0.005) and Beck Depression Inventory (p = 0.046). Of the 13 subjects treated with DCS, 54% had a ≥ 50% HAMD score reduction vs. 15% of the 13 patients randomized to placebo (p = 0.039). A significant (p = 0.043) treatment× pre-treatment glycine serum levels interaction was registered. These findings indicate that NMDAR glycine site antagonism may be a cost-effective target for development of mechanistically novel antidepressants. Larger-sized DCS trials are warranted.

Has an angel shown the way? Etiological and therapeutic implications of the PCP/NMDA model of schizophrenia.

Over the last 20 years, glutamatergic models of schizophrenia have become increasingly accepted as etiopathological models of schizophrenia, based on the observation that phencyclidine (PCP) induces a schizophrenia-like psychosis by blocking neurotransmission at N-methyl-D-aspartate (NMDA)-type glutamate receptors. This article reviews developments in two key predictions of the model: first, that neurocognitive deficits in schizophrenia should follow the pattern of deficit predicted based on underlying NMDAR dysfunction and, second, that agents that stimulate NMDAR function should be therapeutically beneficial. As opposed to dopamine receptors, NMDAR are widely distributed throughout the brain, including subcortical as well as cortical brain regions, and sensory as well as association cortex. Studies over the past 20 years have documented severe sensory dysfunction in schizophrenia using behavioral, neurophysiological, and functional brain imaging approaches, including impaired generation of key sensory-related potentials such as mismatch negativity and visual P1 potentials. Similar deficits are observed in humans following administration of NMDAR antagonists such as ketamine in either humans or animal models. Sensory dysfunction, in turn, predicts impairments in higher order cognitive functions such as auditory or visual emotion recognition. Treatment studies have been performed with compounds acting directly at the NMDAR glycine site, such as glycine, D-serine, or D-cycloserine, and, more recently, with high-affinity glycine transport inhibitors such as RG1678 (Roche). More limited studies have been performed with compounds targeting the redox site. Overall, these compounds have been found to induce significant beneficial effects on persistent symptoms, suggesting novel approaches for treatment and prevention of schizophrenia.

A multicenter, add-on randomized controlled trial of low-dose d-serine for negative and cognitive symptoms of schizophrenia.

BACKGROUND: Observations that antagonists of the N-methyl-d-aspartate (NMDA) receptor of glutamatergic neurons can mimic symptoms of schizophrenia have raised the hope that NMDA agonists can improve symptoms. On the basis of encouraging results of trials in which NMDA agonists were added to antipsychotics, we conducted an adequately powered randomized controlled trial adding d-serine, an NMDA modulator, to antipsychotics. METHOD: This study was a 195-patient, multicenter, double-blind, randomized, placebo-controlled, 16-week trial of d-serine 2 g/d as an add-on treatment to antipsychotics. Subjects had DSM-IV schizophrenia or schizoaffective disorder and were inpatients or outpatients stabilized on antipsychotics, with persistent negative symptoms. The primary outcome measures were changes in negative symptoms and cognition as measured by the Scale for the Assessment of Negative Symptoms (SANS) and the Measurement and Treatment Research to Improve Cognition in Schizophrenia (MATRICS) battery, respectively. The study was performed between 2003 and 2007. RESULTS: Mean total Positive and Negative Syndrome Scale scores at baseline were 75.5. Subjects receiving d-serine and placebo improved in scores on the SANS and MATRICS, but no significant differences were observed between groups: improvement on SANS was 11.4% for d-serine vs 14.8% for placebo, F1,147=1.18, P=.32; and improvement on MATRICS was 6.8% for d-serine vs 6.1% for placebo, F1,125=0.96, P=.39, respectively. d-Serine was well tolerated. DISCUSSION: This study did not find a significant difference between drug and placebo. However, the results are limited by a relatively large placebo response and somewhat lower-achieved doses than in prior studies. Future studies will administer higher doses and will attempt to affect the NMDA receptor using other mechanisms, such as agonists of the presynaptic metabotropic glutamate 2/3 receptor or glycine reuptake inhibitors. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT00138775.

D-serine adjuvant treatment alleviates behavioural and motor symptoms in Parkinson's disease.

Parkinson's disease (PD) manifestations include motor symptoms and behavioural deficits that resemble schizophrenia negative symptoms. The N-methyl-D-aspartate subtype of glutamate receptor (NMDAR) represents a novel pharmacological target in PD. D-serine (DSR) allosterically modulates in-vivo NMDAR-mediated neurotransmission and has been shown to improve negative and antipsychotic drug-induced parkinsonian symptoms in schizophrenia patients. This pilot study assessed DSR effects in ten PD patients who completed a 6-wk double-blind, placebo-controlled, crossover adjuvant treatment trial with 30 mg/kg.d DSR. Primary outcome analyses consisted of separate repeated-measures multivariate analyses of variance for Unified Parkinson's Disease Rating Scale (UPDRS), Simpson-Angus Scale for Extrapyramidal Symptoms (SAS), Abnormal Involuntary Movement Scale (AIMS), and Positive and Negative Syndrome Scale (PANSS) scores. DSR treatment was well tolerated and resulted in increased DSR serum levels (p=0.001) and significantly reduced UPDRS (p=0.02), SAS (p=0.009) and PANSS (0.05) total scores. These preliminary findings suggest that DSR treatment may be beneficial in PD. Larger-sized studies with optimized DSR dosages are warranted.

Preventive pharmacological treatment --an evolving new concept in schizophrenia.

Treatment for schizophrenia remains one of the major challenges of modern medicine. The development of innovative pharmacological approaches for this disorder can potentially alleviate tremendous human suffering and revolutionize mental health delivery systems. While current treatment guidelines for schizophrenia refer to the post-psychosis onset phase of illness, presently there is a strong resurgent interest in secondary prevention intervention applied during schizophrenia prodrome. This development stems largely from the recognition that neurobiological deficit processes associated with schizophrenia severity and chronicity are already active by the time clinical onset is recognized. Proposed preventive treatments include presently used medications and experimental compounds that hypothetically may influence ongoing pathophysiological processes earlier in their development. The future establishment of the early recognition and intervention concept in schizophrenia is critically dependent on the outcome of ongoing research assessing the feasibility of prodrome diagnosis, the efficacy of specific medications and the alleviation of the risks associated with early pharmacological treatment.

Hypnotizability and sensorimotor gating: a dopaminergic mechanism of hypnosis.

Dopaminergic mechanisms have been theorized to influence hypnotizability and sensorimotor gating. In this study, the authors investigated an association between sensorimotor gating, as measured by prepulse inhibition (PPI), and hypnotizability, as assessed by the Stanford Hypnotic Susceptibility Scale, Form C (SHSS:C). They found an inverse correlation between the SSHS:C and PPI. This finding, which replicates an earlier study, provides further evidence for a dopaminergic basis for hypnotizability and suggests additional avenues for research, including a method for possibly enhancing hypnotizability through pharmacological interventions.

Defensive self-presentation style is associated with reduced prepulse inhibition.

Prepulse inhibition (PPI) of the startle response is a cross-species measure of sensorimotor gating that provides a valuable tool for assessing the capacity to effectively screen out irrelevant sensory input. Accumulating evidence suggests that PPI deficits may correlate with impairments in social cognition, i.e. the ability to construct representation about others, oneself and the relations between others and oneself. Social cognition deficits are commonly encountered within the framework of psychiatric disorders. In this study 113 healthy volunteers completed psychopyhsiological measures of sensorimotor gating (PPI) and social self-presentation style (the Concern for Appropriate (CAS) and the Revised Self-Monitoring (RSMS) scales). CAS measures a defensive and fearful social approach aiming at avoiding social threats; RSMS measures an active and flexible social approach aiming at gaining power and status. Analyses revealed an inverse correlation between PPI at the 120 ms prepulse-to-pulse interval and total CAS scores (r=-0.19, p=0.04), as well as with the Attention to Social Comparison Information (ASCI) subscale of the CAS (r=-0.23, p=0.01). These findings suggest that reduced PPI may contribute to the tendency to adopt a defensive and fearful "getting along" social approach. This study is, to our knowledge, the first to assess the relationship between sensorimotor gating and self-presentational style in humans. Its findings suggest that very basic perceptual deficits that can be assessed using the PPI paradigm, may reflect information processing abnormalities that impact negatively upon the perception of complex social interactions.

Shiatsu as an adjuvant therapy for schizophrenia: an open-label pilot study.

CONTEXT: Studies have suggested a possible role for shiatsu in treating a variety of mental and physical ailments. OBJECTIVE: To determine if shiatsu can provide clinical benefit to individuals diagnosed with schizophrenia. DESIGN: An open-label pilot study. SETTING: An inpatient psychiatric ward at Herzog Memorial Hospital, Jerusalem, Israel. PATIENTS: Twelve hospitalized patients with chronic schizophrenia. INTERVENTION: Shiatsu treatment provided in a course of eight 40-minute biweekly sessions over 4 weeks. MAIN OUTCOME MEASURES: All subjects were evaluated at baseline, 2 weeks, 4 weeks (end of treatment), and 12 weeks (followup). The tools used for assessment included the Clinical Global Impression (CGI), the Brief Psychiatric Rating Scale (BPRS), the Positive and Negative Syndrome Scale (PANSS), the Hamilton Rating Scale for Depression (HAM-D), the Hamilton Anxiety Rating Scale (HAM-A), and the Nurses' Observation Scale for Inpatient Evaluation (NOSIE). Side effects were measured using the Simpson-Angus Scale for Extrapyramidal Symptoms (SAS) and the Abnormal Involuntary Movement Scale (AIMS). RESULTS: On all scales of psychopathology and side effects, the subjects showed a statistically and clinically significant improvement by the end of treatment. This improvement was maintained at the 12-week follow-up. These findings, while encouraging, must be considered preliminary and require confirmation and cross-validation in larger-scale controlled studies.

Pilot controlled trial of D-serine for the treatment of post-traumatic stress disorder.

Enhancement of neurotransmission mediated at N-methyl-D-aspartate subtype of glutamate receptors (NMDAR) may be beneficial in post-traumatic stress disorder (PTSD). d-serine (DSR) is an endogenous full agonist at the NMDAR-associated glycine modulatory site. Twenty-two chronic PTSD outpatients were randomly assigned to participate in a 6-wk double-blind, placebo-controlled, crossover trial with 30 mg/kg x d DSR used as monotherapy or add-on pharmacotherapy. Outcome was assessed using the Clinician-Administered PTSD scale (CAPS), Hamilton Anxiety (HAMA) and Depression (HAMD) scales and the civilian version of the Mississippi Scale for Combat-Related PTSD (MISS). DSR treatment was well tolerated and resulted in significantly (p=0.03) increased DSR serum levels. Compared with placebo administration, DSR treatment resulted in significantly reduced HAMA (p=0.007) and MISS (p=0.001) scores and a trend (p=0.07) towards improved CAPS total scores. These preliminary findings indicate that NMDAR glycine site-based pharmacotherapy may be effective in PTSD and warrant larger-sized clinical trials with optimized DSR dosages.