Does the dopamine hypothesis explain schizophrenia?

Adjunctive methylphenidate extended release in patients with schizophrenia: Protocol of a single-centre fixed dose cross-over open-label trial to improve functional and cognitive outcomes

Background

Cognitive symptoms, among the core symptoms of schizophrenia, are associated with poor functional outcome and burden of illness. To date, there is no effective pharmacological treatment for these symptom clusters. Augmentation with psychostimulants has been proposed as a potential treatment option.

Objectives

The present study aims to assess off-label use of adjunctive methylphenidate extended release (ER) in patients with schizophrenia who are stable on antipsychotic medications, and to assess its efficacy on functioning and cognitive outcome.

Methods

This is a single centre study at the Royal Ottawa Mental Health Centre. An open-label fixed dose controlled cross-over trial is planned. Eligible participants will be randomized into one of two arms of the study: 1) four weeks of add-on methylphenidate ER 36 mg, or 2) four weeks of treatment as usual. At 4 weeks, participants will switch arms. The duration of the study includes 8 weeks of treatment and a follow-up visit at 12 weeks. Primary outcome measures include tablet-based tests of functioning and cognition (VRFCAT and BAC) and will be administered at baseline and every 4 weeks. We are aiming to recruit a total of 24 participants.

Expected outcomes

The proposed project intends to assess a potential treatment option for cognitive deficits of schizophrenia, for which there are no recommendations by current treatment guidelines. The novelty and significance of the current study is that it investigates this intervention and assess applicability of it in a "real world setting" in a tertiary care hospital.

Risperidone Decreases Expression of Serotonin Receptor-2A (5-HT2A) and Serotonin Transporter (SERT) but Not Dopamine Receptors and Dopamine Transporter (DAT) in PBMCs from Patients with Schizophrenia

Dopamine and serotonin receptors and transporters play an essential role in the pathophysiology of schizophrenia; changes in their expression have been reported in neurons and leukocytes. Each antipsychotic induces a unique pattern in leukocyte function and phenotype. However, the use of polytherapy to treat schizophrenia makes it challenging to determine the specific effects of risperidone on peripheral blood mononuclear cells (PBMCs). The aim of this study was to evaluate the changes in the expression of D3, D5, DAT, 5-HT2A, and SERT in PBMCs from healthy volunteers (HV), drug-naive patients with schizophrenia (PWS), drug-free PWS, and PWS treated with risperidone for up to 40 weeks using quantitative PCR. Our study revealed elevated mRNA levels of D3, DAT, 5-HT2A, and SERT in unmedicated PWS. Treatment with risperidone led to a reduction only in the expression of 5-HT2A and SERT. Furthermore, we observed a moderate correlation between 5-HT2A expression and the positive and negative syndrome scale (PANSS), as well as SERT expression and PANSS scale. We also found a moderate correlation between 5-HT2A and SERT expression and the positive subscale. The duration of risperidone consumption had a significant negative correlation with the expression of 5-HT2A and SERT. Our study introduces the measurement of 5-HT2A and SERT expression in PBMCs as a useful parameter for assessing the response to risperidone in PWS.

Gestational Exposure to Haloperidol Changes Cdkn1a and Apaf1 mRNA Expressions in Mouse Hippocampus

BACKGROUND

The onset of schizophrenia is associated with both genetic and environmental risks during brain development. Environmental factors during pregnancy can represent risk factors for schizophrenia, and we have previously reported that several microRNA and mRNA expression changes in fetal brains exposed to haloperidol during pregnancy may be related to the onset of this disease. This study aimed to replicate that research and focused on apoptotic-related gene expression changes.

METHODS

Haloperidol (1mg/kg) or aripiprazole (1mg/kg) was injected into pregnant mice. Using RNA sequencing for the hippocampus of each offspring born from pregnant mice exposed to haloperidol, we analyzed genes identified as changed in our previous report and validated two apoptosis-related genes (Cdkn1a and Apaf1) using quantitative polymerase chain reaction (qPCR) methods. Furthermore, we attempted to elucidate the direct effects of haloperidol and aripiprazole on those mRNA expressions in in vitro experiments.

RESULTS

RNA sequencing successfully replicated 16 up-regulated and 5 down-regulated genes in this study. Of those, up-regulations of Cdkn1a and Apaf1 mRNA expression were successfully validated by direct quantification. Moreover, haloperidol and aripiprazole dose-dependent upregulation of both mRNA expressions were confirmed in a Neuro2a cell line.

CONCLUSIONS

In the hippocampus of offspring, intraperitoneal injection of haloperidol to pregnant mice induced up-regulation of apoptotic genes that representing the phenotypic change without apoptosis. These findings will be useful for understanding the molecular biological mechanisms underlying the effects of antipsychotics on the fetal brain.

Sonic hedgehog pathway as a new target of atypical antipsychotics: Revisiting of amisulpride and aripiprazole effects in a rat model of schizophrenia

OBJECTIVES

Schizophrenia is a chronic mental illness presented by cognitive deficits that precede its positive and negative symptoms. Sonic hedgehog (Shh)-pathway contributes to its pathophysiology. Shh has a role in neurogenesis as it regulates proliferation and survival of neural cells. In this study, effects of the anti-psychotics Amisulpride and/or Aripiprazole on the Shh-pathway and its relation to cognitive functions and neurogenesis in a rat model of schizophrenia were tested.

METHODS

60 male Wistar rats were allocated into the following groups: control, socially isolated, amisulpride and/or aripiprazole-treated groups. Rats were then subjected to behavioral, biochemical, and histopathological tests to assess the impact of these drugs on Shh-pathway.

KEY FINDINGS

Cognitive-dysfunction was evidenced in socially isolated group in novel object, three-chamber, and Morris water maze tests, associated by disorganised Shh-pathway proteins levels concentrations, increased glial fibrillary acidic protein (GFAP)-stained astrocytes. Treated groups favorably reversed these changes evidenced by increased Shh, transmembrane patched-1 and smoothened, glioma-associated-oncogene (GLI)-1 levels, dopamine-1 receptors and brain derived neurotrophic factor, and decreased GLI-3 protein, GFAP immune reaction in astrocytes and inflammatory markers compared to socially isolated group.

CONCLUSION

Amisulpride and/or aripiprazole have a favorable role in turning on Shh-pathway with subsequent beneficial cognitive and neurogenesis effects.

MicroRNA schizophrenia: Etiology, biomarkers and therapeutic targets

The three sets of symptoms associated with schizophrenia-positive, negative, and cognitive-are burdensome and have serious effects on public health, which affects up to 1% of the population. It is now commonly believed that in addition to the traditional dopaminergic mesolimbic pathway, the etiology of schizophrenia also includes neuronal networks, such as glutamate, GABA, serotonin, BDNF, oxidative stress, inflammation and the immune system. Small noncoding RNA molecules called microRNAs (miRNAs) have come to light as possible participants in the pathophysiology of schizophrenia in recent years by having an impact on these systems. These small RNAs regulate the stability and translation of hundreds of target transcripts, which has an impact on the entire gene network. There may be improved approaches to treat and diagnose schizophrenia if it is understood how these changes in miRNAs alter the critical related signaling pathways that drive the development and progression of the illness.

Xanomeline-Trospium and Muscarinic Involvement in Schizophrenia

Schizophrenia is a severe mental illness that has its onset in late adolescence or early adulthood and is associated with significant dysfunction across multiple domains. The pathogenesis of schizophrenia remains unknown, but physiologic understanding of the illness has been driven by the dopamine hypothesis. However, acetylcholine (ACh) clearly plays a role with mixed results regarding effect on psychosis. Selective muscarinic M₁ and M₄ agonists, such as xanomeline, originally developed to aid in cognitive loss with Alzheimer's, showed promise in proof-of-concept study in 20 patients with schizophrenia. Unfortunately, tolerability problems made muscarinic agonists impractical in either condition. However, coadministration of trospium, a lipophobic, non-selective muscarinic antagonist previously used for the treatment of overactive bladder, with xanomeline resulted in a significant reduction of cholinergic adverse effects. A recent randomized, placebo-controlled study of the antipsychotic effects of this combination in 182 patients with acute psychosis revealed improved tolerability with 80% of subjects staying to the end of the 5 weeks study. At the end of the trial, the treatment group saw a -17.4 change in the positive and negative symptom scale (PANSS) score from baseline compared to a -5.9 change in the placebo arm (P < 0.001). Furthermore, the negative symptom subscore, was also superior in the active arm (P < 0.001). These early studies are exciting because they suggest that the cholinergic system may be recruited to treat a severe and disabling disorder with suboptimal treatment options. Xanomeline-trospium combination is currently in phase III studies.

Antipsychotic- and Anxiolytic-like Properties of a Multimodal Compound JJGW08 in Rodents

Schizophrenia is a chronic mental illness, which remains difficult to treat. A high resistance to the available therapies, their insufficient efficacy, and numerous side effects are the reasons why there is an urgent need to develop new antipsychotics. This study aimed to assess the antipsychotic-like effects of JJGW08, a novel arylpiperazine alkyl derivative of salicylamide, in rodents. First, considering the JJGW08 receptor profile, we investigated the compound's intrinsic activity towards dopamine D₂ and serotonin 5-HT_1A, 5-HT_2A, and 5-HT₇ receptors using functional assays. Next, we assessed the effect of JJGW08 on MK-801- and amphetamine-induced hyperlocomotion, its risk of inducing catalepsy and impairing motor coordination, as well as the anxiolytic-like effects in the four-plate and marble burying tests in mice. Finally, we investigated the antipsychotic-like properties of JJGW08 in rats using MK-801-induced hyperlocomotion and prepulse inhibition tests. We found that JJGW08 showed antagonistic properties at dopamine D₂ and serotonin 5-HT_1A, 5-HT_2A, and 5-HT₇ receptors. However, the effect on the 5-HT_2A and 5-HT₇ receptors was very weak. Moreover, the tested compound showed an antipsychotic-like effect in MK-801- and amphetamine-induced hyperlocomotion but not in a prepulse inhibition test in rats. Notably, JJGW08 demonstrated anxiolytic-like properties in both behavioral tests. Importantly, the compound did not induce catalepsy or motor coordination impairment in mice at antipsychotic-like doses. Our study suggests it is worth searching for new potential antipsychotics among arylpiperazine alkyl derivatives of salicylamide.

Why haven't we solved the addiction crisis?

The current addiction crisis has destroyed a multitude of lives, leaving millions of fatalities worldwide in its wake. At the same time, various governmental agencies dedicated to solving this seemingly never-ending dilemma have not yet succeeded or delivered on their promises. We understand that addictive behavioral seeking is a multi-faceted neurobiological and spiritually complicated phenomenon. However, although the substitution replacement approach, especially to treat Opioid Use Disorder (OUD), has importance for harm reduction in the short term, it does not bring about a harm-free recovery or prevention. Instead, we propose a promising novel approach that uses genetic risk testing with induction of dopamine homeostasis and an objective Brain Health Check during youth. Our model involves a six-hit approach known as the "Reward Dysregulation Syndrome Solution System," which can identify addiction risk and target the root cause of addiction, dopamine dysregulation. While we applaud all past sophisticated neurogenetic and neuropharmacological research, our opinion is that in the long term, addiction scientists and clinicians might characterize preaddiction using tests; for example, administering the validated RDSQuestionarre29, genetic risk assessment, a modified brain health check, or diagnostic framing of mild to moderate Substance Use Disorder (SUD). The preaddiction concept could incentivize the development of interventions to prevent addiction from developing in the first place and target and treat neurotransmitter imbalances and other early indications of addiction. WC 222.

Insights into the Promising Prospect of G Protein and GPCR-Mediated Signaling in Neuropathophysiology and Its Therapeutic Regulation

G protein-coupled receptors (GPCRs) are intricately involved in the conversion of extracellular feedback to intracellular responses. These specialized receptors possess a crucial role in neurological and psychiatric disorders. Most nonsensory GPCRs are active in almost 90% of complex brain functions. At the time of receptor phosphorylation, a GPCR pathway is essentially activated through a G protein signaling mechanism via a G protein-coupled receptor kinase (GRK). Dopamine, an important neurotransmitter, is primarily involved in the pathophysiology of several CNS disorders; for instance, bipolar disorder, schizophrenia, Parkinson's disease, and ADHD. Since dopamine, acetylcholine, and glutamate are potent neuropharmacological targets, dopamine itself has potential therapeutic effects in several CNS disorders. GPCRs essentially regulate brain functions by modulating downstream signaling pathways. GPR6, GPR52, and GPR8 are termed orphan GPCRs because they colocalize with dopamine D1 and D2 receptors in neurons of the basal ganglia, either alone or with both receptors. Among the orphan GPCRs, the GPR52 is recognized for being an effective psychiatric receptor. Various antipsychotics like aripiprazole and quetiapine mainly target GPCRs to exert their actions. One of the most important parts of signal transduction is the regulation of G protein signaling (RGS). These substances inhibit the activation of the G protein that initiates GPCR signaling. Developing a combination of RGS inhibitors with GPCR agonists may prove to have promising therapeutic potential. Indeed, several recent studies have suggested that GPCRs represent potentially valuable therapeutic targets for various psychiatric disorders. Molecular biology and genetically modified animal model studies recommend that these enriched GPCRs may also act as potential therapeutic psychoreceptors. Neurotransmitter and neuropeptide GPCR malfunction in the frontal cortex and limbic-related regions, including the hippocampus, hypothalamus, and brainstem, is likely responsible for the complex clinical picture that includes cognitive, perceptual, emotional, and motor symptoms. G protein and GPCR-mediated signaling play a critical role in developing new treatment options for mental health issues, and this study is aimed at offering a thorough picture of that involvement. For patients who are resistant to current therapies, the development of new drugs that target GPCR signaling cascades remains an interesting possibility. These discoveries might serve as a fresh foundation for the creation of creative methods for pharmacologically useful modulation of GPCR function.

Neuropathological studies of serotonergic and noradrenergic systems in Lewy body disease patients with delusion or depression

AIM

The association between psychiatric symptoms in Lewy body disease (LBD) and the noradrenergic and serotonergic systems is still controversial. This study investigated the quantitative relationships of depression and delusion with these systems.

METHODS

We studied 24 postmortem tissues from individuals with a pathological diagnosis of LBD with sufficient clinical history. The numbers of neurons and Lewy bodies (LBs) in the locus coeruleus (LC) and dorsal raphe nucleus (DRN) were counted, and the density of neurons in the DRN was analyzed. In addition, the densities of tryptophan hydroxylase-positive neurites and norepinephrine transporter-positive neurites in the amygdala and dorsal prefrontal cortex were measured. Finally, we divided the cases into two groups: with or without depressive mood, and with or without delusion. Quantitative histological data were compared between the groups.

RESULTS

The group with depressive mood had a significantly smaller number of neurons in the LC compared with the group without depressive mood. The group with delusion had a significantly larger number of LBs in the DRN compared with the group without delusion. The density of norepinephrine transporter-positive neurites in the dorsal prefrontal cortex was significantly correlated with the number of neurons in the LC.

CONCLUSIONS

The accumulation of LBs in the DRN of individuals with LBD was associated with delusion, whereas a decrease in the number of neurons in the LC was associated with depressive mood. These neurodegenerative changes involved the serotonergic and noradrenergic systems and may be associated with the formation of delusion and depression, respectively, in LBD.

Ketamine use disorder: preclinical, clinical, and neuroimaging evidence to support proposed mechanisms of actions

Ketamine, a noncompetitive NMDA receptor antagonist, has been exclusively used as an anesthetic in medicine and has led to new insights into the pathophysiology of neuropsychiatric disorders. Clinical studies have shown that low subanesthetic doses of ketamine produce antidepressant effects for individuals with depression. However, its use as a treatment for psychiatric disorders has been limited due to its reinforcing effects and high potential for diversion and misuse. Preclinical studies have focused on understanding the molecular mechanisms underlying ketamine's antidepressant effects, but a precise mechanism had yet to be elucidated. Here we review different hypotheses for ketamine's mechanism of action including the direct inhibition and disinhibition of NMDA receptors, AMPAR activation, and heightened activation of monoaminergic systems. The proposed mechanisms are not mutually exclusive, and their combined influence may exert the observed structural and functional neural impairments. Long term use of ketamine induces brain structural, functional impairments, and neurodevelopmental effects in both rodents and humans. Its misuse has increased rapidly in the past 20 years and is one of the most common addictive drugs used in Asia. The proposed mechanisms of action and supporting neuroimaging data allow for the development of tools to identify 'biotypes' of ketamine use disorder (KUD) using machine learning approaches, which could inform intervention and treatment.

Prospective, observational, single-centre cohort study with an independent control group matched for age and sex aimed at investigating the significance of cholinergic activity in patients with schizophrenia: study protocol of the CLASH-study

INTRODUCTION

Alterations in the cholinergic metabolism may cause various clinical symptoms of schizophrenia. In addition to the 'monoamine hypothesis,' neuroinflammation is also discussed as a cause of schizophrenia. To date, there has been no evidence of alterations in the central cholinergic transmitter balance in patients with schizophrenia under clinical conditions. By contrast, studies in critically ill patients have established the measurement of acetylcholinesterase activity as a suitable surrogate parameter of central cholinergic transmitter balance/possible pathophysiological changes. Butyrylcholinesterase activity has been established as a parameter indicating possible (neuro)inflammatory processes. Both parameters can now be measured using a point-of-care approach. Therefore, the primary objective of this study is to investigate whether acetylcholinesterase and butyrylcholinesterase activity differs in patients with various forms of schizophrenia. Secondary objectives address the possible association between acetylcholinesterase and butyrylcholinesterase activity and (1) schizophrenic symptoms using the Positive and Negative Syndrome Scale, (2) the quantity of antipsychotics taken and (3) the duration of illness.

METHODS AND ANALYSIS

The study is designed as a prospective, observational cohort study with one independent control group. It is being carried out at the Department of Psychiatry and Psychotherapy III, Ulm University Hospital, Germany. Patient enrolment started in October 2020, and the anticipated end of the study is in January 2022. The enrolment period was set from October 2020 to December 2021 (extension required due to SARS-CoV-2 pandemic). The sample size is calculated at 50 patients in each group. Esterase activity is measured on hospital admission (acute symptomatology) and after referral to a postacute ward over a period of three consecutive days. The matched control group will be created after reaching 50 patients with schizophrenia. This will be followed by a comprehensive statistical analysis of the data set.

ETHICS AND DISSEMINATION

The study was registered prospectively in the German Clinical Trials Register (DRKS-ID: DRKS00023143,URL: https://www.drks.de/drks_web/navigate.do?navigationId=trial.HTML&TRIAL_ID=DRKS00023143) after approval by the ethics committee of the University of Ulm, Germany Trial Code No. 280/20.

TRIAL REGISTRATION NUMBER

DRKS00023143; Pre-results.

Does nicotine exposure during adolescence modify the course of schizophrenia-like symptoms? Behavioral analysis in a phencyclidine-induced mice model

The first symptoms of schizophrenia (SCHZ) are usually observed during adolescence, a developmental period during which first exposure to psychoactive drugs also occurs. These epidemiological findings point to adolescence as critical for nicotine addiction and SCHZ comorbidity, however it is not clear whether exposure to nicotine during this period has a detrimental impact on the development of SCHZ symptoms since there is a lack of studies that investigate the interactions between these conditions during this period of development. To elucidate the impact of a short course of nicotine exposure across the spectrum of SCHZ-like symptoms, we used a phencyclidine-induced adolescent mice model of SCHZ (2.5mg/Kg, s.c., daily, postnatal day (PN) 38-PN52; 10mg/Kg on PN53), combined with an established model of nicotine minipump infusions (24mg/Kg/day, PN37-44). Behavioral assessment began 4 days after the end of nicotine exposure (PN48) using the following tests: open field to assess the hyperlocomotion phenotype; novel object recognition, a declarative memory task; three-chamber sociability, to verify social interaction and prepulse inhibition, a measure of sensorimotor gating. Phencyclidine exposure evoked deficits in all analyzed behaviors. Nicotine history reduced the magnitude of phencyclidine-evoked hyperlocomotion and impeded the development of locomotor sensitization. It also mitigated the deficient sociability elicited by phencyclidine. In contrast, memory and sensorimotor gating deficits evoked by phencyclidine were neither improved nor worsened by nicotine history. In conclusion, our results show for the first time that nicotine history, restricted to a short period during adolescence, does not worsen SCHZ-like symptoms evoked by a phencyclidine-induced mice model.

In Silico Repositioning of Dopamine Modulators with Possible Application to Schizophrenia: Pharmacophore Mapping, Molecular Docking and Molecular Dynamics Analysis

We have performed theoretical calculations with 70 drugs that have been considered in 231 clinical trials as possible candidates to repurpose drugs for schizophrenia based on their interactions with the dopaminergic system. A hypothesis of shared pharmacophore features was formulated to support our calculations. To do so, we have used the crystal structure of the D2-like dopamine receptor in complex with risperidone, eticlopride, and nemonapride. Linagliptin, citalopram, flunarizine, sildenafil, minocycline, and duloxetine were the drugs that best fit with our model. Molecular docking calculations, molecular dynamics outcomes, blood-brain barrier penetration, and human intestinal absorption were studied and compared with the results. From the six drugs selected in the shared pharmacophore features input, flunarizine showed the best docking score with D2, D3, and D4 dopamine receptors and had high stability during molecular dynamics simulations. Flunarizine is a frequently used medication to treat migraines and vertigo. However, its antipsychotic properties have been previously hypothesized, particularly because of its possible ability to block the D2 dopamine receptors.

Stem cell-based models and therapies: a key approach into schizophrenia treatment

Psychiatric disorders such as schizophrenia can generate distress and disability along with heavy costs on individuals and health care systems. Different genetic and environmental factors play a pivotal role in the appearance of the mentioned disorders. Since the conventional treatment options for psychiatric disorders are suboptimal, investigators are trying to find novel strategies. Herein, stem cell therapies have been recommended as novel choices. In this context, the preclinical examination of stem cell-based therapies specifically using appropriate models can facilitate passing strong filters and serious examination to ensure proper quality and safety of them as a novel treatment approach. Animal models cannot be adequately helpful to follow pathophysiological features. Nowadays, stem cell-based models, particularly induced pluripotent stem cells reflected as suitable alternative models in this field. Accordingly, the importance of stem cell-based models, especially to experiment with the regenerative medicine outcomes for schizophrenia as one of the severe typing of psychiatric disorders, is addressed here.

Beyond the Mind-Serum Trace Element Levels in Schizophrenic Patients: A Systematic Review

The alterations in serum trace element levels are common phenomena observed in patients with different psychiatric conditions such as schizophrenia, autism spectrum disorder, or major depressive disorder. The fluctuations in the trace element concentrations might act as potential diagnostic and prognostic biomarkers of many psychiatric and neurological disorders. This paper aimed to assess the alterations in serum trace element concentrations in patients with a diagnosed schizophrenia. The authors made a systematic review, extracting papers from the PubMed, Web of Science, and Scopus databases according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Among 5009 articles identified through database searching, 59 of them were assessed for eligibility. Ultimately, 33 articles were included in the qualitative synthesis. This review includes the analysis of serum levels of the following trace elements: iron, nickel, molybdenum, phosphorus, lead, chromium, antimony, uranium, magnesium, aluminum, zinc, copper, selenium, calcium, and manganese. Currently, there is no consistency regarding serum trace element levels in schizophrenic patients. Thus, it cannot be considered as a reliable prognostic or diagnostic marker of schizophrenia. However, it can be assumed that altered concentrations of those elements are crucial regarding the onset and exaggeration of either psychotic or negative symptoms or cognitive dysfunctions.

Multi-targeted drug design strategies for the treatment of schizophrenia

INTRODUCTION

Schizophrenia is a complex psychiatric disease (or a conglomeration of disorders) manifesting with positive, negative and cognitive symptoms. The pathophysiology of schizophrenia is not completely known; however, it involves many neurotransmitters and their receptors. In order to treat schizophrenia, drugs need to be multi-target drugs. Indeed, the action of second and third generation antipsychotics involves interactions with many receptors, belonging mainly to aminergic GPCRs.

AREAS COVERED

In this review, the authors summarize current concepts of schizophrenia with the emphasis on the modern dopaminergic, serotoninergic, and glutamatergic hypotheses. Next, they discuss treatments of the disease, stressing multi-target antipsychotics. They cover different aspects of design of multi-target ligands, including the application of molecular modeling approaches for the design and benefits and limitations of multifunctional compounds. Finally, they present successful case studies of multi-target drug design against schizophrenia.

EXPERT OPINION

Treatment of schizophrenia requires the application of multi-target drugs. While designing single target drugs is relatively easy, designing multifunctional compounds is a challenge due to the necessity to balance the affinity to many targets, while avoiding promiscuity and the problems with drug-likeness. Multi-target drugs bring many benefits: better efficiency, fewer adverse effects, and drug-drug interactions and better patient compliance to drug regime.

Fine structure analysis of perineuronal nets in the ketamine model of schizophrenia

Perineuronal nets (PNNs) represent a highly condensed specialized form of brain extracellular matrix (ECM) enwrapping mostly parvalbumin-positive interneurons in the brain in a mesh-like fashion. PNNs not only regulate the onset and completion of the critical period during postnatal brain development, control cell excitability, and synaptic transmission but are also implicated in several brain disorders including schizophrenia. Holes in the perineuronal nets, harboring the synaptic contacts, along with hole-surrounding ECM barrier can be viewed as PNN compartmentalization units that might determine the properties of synapses and heterosynaptic communication. In this study, we developed a novel open-source script for Fiji (ImageJ) to semi-automatically quantify structural alterations of PNNs such as the number of PNN units, area, mean intensity of PNN marker expression in 2D and 3D, shape parameters of PNN units in the ketamine-treated Sprague-Dawley rat model of schizophrenia using high-resolution confocal microscopic images. We discovered that the mean intensity of ECM within PNN units is inversely correlated with the area and the perimeter of the PNN holes. The intensity, size, and shape of PNN units proved to be three major principal factors to describe their variability. Ketamine-treated rats had more numerous but smaller and less circular PNN units than control rats. These parameters allowed to correctly classify individual PNNs as derived from control or ketamine-treated groups with ≈85% reliability. Thus, the proposed multidimensional analysis of PNN units provided a robust and comprehensive morphometric fingerprinting of fine ECM structure abnormalities in the experimental model of schizophrenia.

Perturbations in the catecholamine metabolism and protective effect of "3-(3, 4-dimethoxy phenyl)-1-4(methoxy phenyl) prop-2-en-1-one" during ketamine-induced schizophrenia: an in vivo and in silico studies

Different kinds of secondary metabolites present in the medicinal plants play an important role to alleviate different human ailments including neurodegenerative disorders such as Parkinson's, Alzheimer's, epilepsy and schizophrenia etc. Recently we have isolated and characterized a novel bioactive compound viz. 3-(3,4-dimethoxy phenyl)-1-4(methoxy phenyl)prop-2-en-1-one from the methanolic extract of Celastrus paniculatus (CP) which has been widely used for the treatment of neurodegenerative diseases. The present investigation is mainly aimed to evaluate the neuroprotective potential of the above bioactive compound against ketamine-induced schizophrenia with particular reference to catecholaminergic metabolism using in vivo and in silico methods. Ketamine-induced schizophrenia caused significant elevation in biogenic amines (epinephrine, nor epinephrine, dopamine and 5-HT) and monoamine oxidase activity levels which were restored to normal during the treatment with the bioactive compound akin to the reference compound, clozapine. In addition, the compound has shown highest binding score against all the biogenic amine receptors viz. D1, D2, D3, D4 and serotonin receptor, 5-HT_2A with lowest inhibition constant values than the reference compound, clozapine. The present findings suggest that modulation of CNS monoamine neurotransmitter system might partly contribute to the impairments associated with schizophrenia and the plant compound alleviates the monoaminergic abnormalities associated with the neurological dysfunction.Communicated by Ramaswamy H. Sarma.

Alterations of Astrocytes in the Context of Schizophrenic Dementia

The levels of the astrocyte markers (GFAP, S100B) were increased unevenly in patients with schizophrenia. Reactive astrogliosis was found in approximately 70% of patients with schizophrenia. The astrocytes play a major role in etiology and pathogenesis of schizophrenia. Astrocytes produce the components that altered in schizophrenia extracellular matrix system which are involved in inflammation, functioning of interneurons, glio-, and neurotransmitter system, especially glutamate system. Astrocytes activate the interneurons through glutamate release and ATP. Decreased expression of astrocyte glutamate transporters was observed in patients with schizophrenia. Astrocytes influence on N-methyl-d-aspartate (NMDA) receptors via D-serine, an agonist of the glycine-binding site of NMDA receptors, and kynurenic acid, an endogenous antagonist. NMDA receptors, on its turn, control the impulses of dopamine neurons. Therefore following theories of schizophrenia are proposed. They are a) activation of astrocytes for neuroinflammation, b) glutamate and dopamine theory, as astrocyte products control the activity of NMDA receptors, which influence on the dopamine neurons.

A pilot study of biomarkers of oxidative stress in serum and schizophrenia

Increasing evidence indicates that oxidative damage and inflammation is present in patients with schizophrenia. In this study, we investigated the association between the serum concentrations of four typical oxidative stress and inflammatory biomarkers (monocyte chemotactic protein-1, heme oxygenase-1, interleukin-8, and 8-Hydroxydeoxyguanine) and schizophrenia using a case-control study design. In total, 44 patients with schizophrenia and 45 normal controls from Shandong Province, China were recruited. Fasting blood samples were collected from all participants and the serum concentration of the four biomarkers were analyzed by Enzyme-linked immunosorbent assay. The concentrations of monocyte chemotactic protein-1 and interleukin-8 were significantly higher in the patients than in the controls, while there was no significant difference in the serum concentrations of heme oxygenase-1 and 8-Hydroxydeoxyguanine. Moreover, the serum concentrations of monocyte chemotactic protein-1 and interleukin-8 in patients were positively correlated with severity of clinical symptoms. Dose-response relationships between serum biomarker concentrations and schizophrenia were observed. This study suggests that levels of monocyte chemotactic protein-1 and interleukin-8 are increased in patients with schizophrenia and correlated with positive symptom severity.

In Vitro and In Vivo Models for the Investigation of Potential Drugs Against Schizophrenia

Schizophrenia (SZ) is a complex psychiatric disorder characterized by positive, negative, and cognitive symptoms, and is not satisfactorily treated by current antipsychotics. Progress in understanding the basic pathomechanism of the disease has been hampered by the lack of appropriate models. In order to develop modern drugs against SZ, efficient methods to study them in in vitro and in vivo models of this disease are required. In this review a short presentation of current hypotheses and concepts of SZ is followed by a description of current progress in the field of SZ experimental models. A critical discussion of advantages and limitations of in vitro models and pharmacological, genetic, and neurodevelopmental in vivo models for positive, negative, and cognitive symptoms of the disease is provided. In particular, this review concerns the important issue of how cellular and animal systems can help to meet the challenges of modeling the disease, which fully manifests only in humans, as experimental studies of SZ in humans are limited. Next, it is emphasized that novel clinical candidates should be evaluated in animal models for treatment-resistant SZ. In conclusion, the plurality of available in vitro and in vivo models is a consequence of the complex nature of SZ, and there are extensive possibilities for their integration. Future development of more efficient antipsychotics reflecting the pleiotropy of symptoms in SZ requires the incorporation of various models into one uniting model of the multifactorial disorder and use of this model for the evaluation of new drugs.

A Peptide Link Between Human Cytomegalovirus Infection, Neuronal Migration, and Psychosis

Alongside biological, psychological, and social risk factors, psychotic syndromes may be related to disturbances of neuronal migration. This highly complex process characterizes the developing brain of the fetus, the early postnatal brain, and the adult brain, as reflected by changes within the subventricular zone and the dentate gyrus of the hippocampus, where neurogenesis persists throughout life. Psychosis also appears to be linked to human cytomegalovirus (HCMV) infection. However, little is known about the connection between psychosis, HCMV infection, and disruption of neuronal migration. The present study addresses the hypothesis that HCMV infection may lead to mental disorders through mechanisms of autoimmune cross-reactivity. Searching for common peptides that underlie immune cross-reactions, the analyses focus on HCMV and human proteins involved in neuronal migration. Results demonstrate a large overlap of viral peptides with human proteins associated with neuronal migration, such as ventral anterior homeobox 1 and cell adhesion molecule 1 implicated in GABAergic and glutamatergic neurotransmission. The present findings support the possibility of immune cross-reactivity between HCMV and human proteins that-when altered, mutated, or improperly functioning-may disrupt normal neuronal migration. In addition, these findings are consistent with a molecular and mechanistic framework for pathological sequences of events, beginning with HCMV infection, followed by immune activation, cross-reactivity, and neuronal protein variations that may ultimately contribute to the emergence of mental disorders, including psychosis.

Cannabis and Psychosis Through the Lens of DSM-5

Evidence for an association between cannabis and psychosis has been documented in literature in many forms including experimental studies, epidemiological data, and case series. The association has implications for psychotic outcomes ranging from mild to severe and occurring over minutes to years. Due to the huge variety of exposures and outcome measures reported, creating a coherent account of all the available information is difficult. A useful way to conceptualize these wide-ranging results is to consider the association between cannabis and psychosis as it occurs within the context of widely used DSM-5 diagnoses. In the present review we examine cannabis/psychosis associations as they pertain to Cannabis Intoxication, Cannabis-Induced Psychotic Disorder, and Schizophrenia. This allows for an understanding of the cannabis and psychosis association along something approaching a continuum. Cannabis intoxication becomes Cannabis-Induced Psychotic Disorder once certain severity and duration criteria are met and Cannabis-Induced Psychotic Disorder is heavily associated with future schizophrenia diagnoses.

Generation and Characterization of Induced Pluripotent Stem Cells from Mononuclear Cells in Schizophrenic Patients

Objective

Schizophrenia (SZ) is a mental disorder in which psychotic symptoms are the main problem. The pathogenesis of SZ is not fully understood, partly because of limitations in current disease models and technology. The development of induced pluripotent stem cell (iPSC) technology has opened up the possibility of elucidating disease mechanisms in neurodegenerative diseases. Here, we aimed to obtain iPSCs from peripheral blood mononuclear cells (PBMCs) of normal and schizophrenic individuals and analyze the inflammatory response in these iPSCs.

Materials and Methods

In this experimental study, we isolated PBMCs from whole blood of healthy individuals and SZ patients and reprogrammed them into iPSCs by transfection of recombinant lentiviruses that contained Yamanaka factors (Oct4, Sox2, Klf4 and c-Myc). We calculated the numbers of iPSC clones and stained them with alkaline phosphatase (ALP), Nanog, SSEA4, Nestin, Vimentin, and AFP to confirm their efficiency and pluripotency. The iPSCs were analyzed by real-time quantitative polymerase chain reaction (qRT-PCR) for the expressions of inflammatory factors.

Results

iPSCs from schizophrenic patients (SZ-iPSCs) exhibited typical morphology and highly expressed pluripotent markers. These iPSCs retained their normal karyotype and differentiated in vitro to form embryoid bodies (EBs) that expressed markers of all 3 germ layers. However, iPSCs from the SZ-iPSCs group had a weak capacity to differentiate into ectoderm compared to the normal iPSCs (Con-iPSC). An elevated, stronger inflammatory response existed in iPSCs from schizophrenic individuals.

Conclusion

We successfully obtained iPSCs from PBMCs of schizophrenic patients without genetic operation and analyzed the expressions of pluripotent markers and inflammatory factors between the Con-iPSC and SZ-iPSC groups. Taken together, our results may assist to explain the pathogenesis of SZ and develop new strategies for clinical diagnosis and treatment.

Confused Connections? Targeting White Matter to Address Treatment Resistant Schizophrenia

Despite development of comprehensive approaches to treat schizophrenia and other psychotic disorders and improve outcomes, there remains a proportion (approximately one-third) of patients who are treatment resistant and will not have remission of psychotic symptoms despite adequate trials of pharmacotherapy. This level of treatment response is stable across all stages of the spectrum of psychotic disorders, including early phase psychosis and chronic schizophrenia. Our current pharmacotherapies are beneficial in decreasing positive symptomology in most cases, however, with little to no impact on negative or cognitive symptoms. Not all individuals with treatment resistant psychosis unfortunately, even benefit from the potential pharmacological reductions in positive symptoms. The existing pharmacotherapy for psychosis is targeted at neurotransmitter receptors. The current first and second generation antipsychotic medications all act on dopamine type 2 receptors with the second generation drugs also interacting significantly with serotonin type 1 and 2 receptors, and with varying pharmacodynamic profiles overall. This focus on developing dopaminergic/serotonergic antipsychotics, while beneficial, has not reduced the proportion of patients experiencing treatment resistance to date. Another pharmacological approach is imperative to address treatment resistance both for response overall and for negative symptoms in particular. There is research suggesting that changes in white matter integrity occur in schizophrenia and these may be more associated with cognition and even negative symptomology. Here we review the evidence that white matter abnormalities in the brain may be contributing to the symptomology of psychotic disorders. Additionally, we propose that white matter may be a viable pharmacological target for pharmacoresistant schizophrenia and discuss current treatments in development for schizophrenia that target white matter.

Multi-Target Approach for Drug Discovery against Schizophrenia

Polypharmacology is nowadays considered an increasingly crucial aspect in discovering new drugs as a number of original single-target drugs have been performing far behind expectations during the last ten years. In this scenario, multi-target drugs are a promising approach against polygenic diseases with complex pathomechanisms such as schizophrenia. Indeed, second generation or atypical antipsychotics target a number of aminergic G protein-coupled receptors (GPCRs) simultaneously. Novel strategies in drug design and discovery against schizophrenia focus on targets beyond the dopaminergic hypothesis of the disease and even beyond the monoamine GPCRs. In particular these approaches concern proteins involved in glutamatergic and cholinergic neurotransmission, challenging the concept of antipsychotic activity without dopamine D₂ receptor involvement. Potentially interesting compounds include ligands interacting with glycine modulatory binding pocket on N-methyl-d-aspartate (NMDA) receptors, positive allosteric modulators of α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, positive allosteric modulators of metabotropic glutamatergic receptors, agonists and positive allosteric modulators of α7 nicotinic receptors, as well as muscarinic receptor agonists. In this review we discuss classical and novel drug targets for schizophrenia, cover benefits and limitations of current strategies to design multi-target drugs and show examples of multi-target ligands as antipsychotics, including marketed drugs, substances in clinical trials, and other investigational compounds.

Current Concepts and Treatments of Schizophrenia

Schizophrenia is a debilitating mental illness which involves three groups of symptoms, i.e., positive, negative and cognitive, and has major public health implications. According to various sources, it affects up to 1% of the population. The pathomechanism of schizophrenia is not fully understood and current antipsychotics are characterized by severe limitations. Firstly, these treatments are efficient for about half of patients only. Secondly, they ameliorate mainly positive symptoms (e.g., hallucinations and thought disorders which are the core of the disease) but negative (e.g., flat affect and social withdrawal) and cognitive (e.g., learning and attention disorders) symptoms remain untreated. Thirdly, they involve severe neurological and metabolic side effects and may lead to sexual dysfunction or agranulocytosis (clozapine). It is generally agreed that the interactions of antipsychotics with various neurotransmitter receptors are responsible for their effects to treat schizophrenia symptoms. In particular, several G protein-coupled receptors (GPCRs), mainly dopamine, serotonin and adrenaline receptors, are traditional molecular targets for antipsychotics. Comprehensive research on GPCRs resulted in the exploration of novel important signaling mechanisms of GPCRs which are crucial for drug discovery: intentionally non-selective multi-target compounds, allosteric modulators, functionally selective compounds and receptor oligomerization. In this review, we cover current hypotheses of schizophrenia, involving different neurotransmitter systems, discuss available treatments and present novel concepts in schizophrenia and its treatment, involving mainly novel mechanisms of GPCRs signaling.

Albizia zygia root extract exhibits antipsychotic-like properties in murine models of schizophrenia

BACKGROUND

The root extract of Albizia zygia (DC.) J.F. Macbr. (Leguminosae) is used to manage mental disorders in African traditional medicine. However, its value, particularly, against negative and cognitive symptoms of schizophrenia have not been evaluated.

AIM

The aim of this study was to evaluate the antipsychotic properties of the hydroethanolic root extract of Albizia zygia (AZE) against positive, negative and cognitive symptoms of schizophrenia in animal models.

MATERIALS AND METHODS

The effects of AZE (30-300 mg kg^-1) were evaluated against apomorphine-induced cage climbing as well as ketamine -induced hyperlocomotion, -enhanced immobility, -impaired social interaction and novel object recognition. The propensity of AZE to induce catalepsy and to attenuate haloperidol-induced catalepsy were also investigated.

RESULTS

AZE 30-300 mg kg^-1 significantly reduced apomorphine-induced climbing behaviour as well as ketamine-induced hyperlocomotion, immobility and object recognition deficits (at least P < 0.05). Moreover, the extract showed no cataleptic effect but significantly inhibited haloperidol-induced catalepsy at a dose of 30 mg kg^-1 (P < 0.05).

CONCLUSION

The root extract of Albizia zygia exhibited an antipsychotic-like activity in mice with potential to alleviate positive, negative and cognitive symptoms of schizophrenia.

d-Serine administration affects nitric oxide synthase 1 adaptor protein and DISC1 expression in sex-specific manner

Antipsychotic medications are inefficient at treating symptoms of schizophrenia (SCZ), and N-methyl d-aspartate receptor (NMDAR) agonists are potential therapeutic alternatives. As such, these agonists may act on different pathways and proteins altered in the brains of patients with SCZ than do antipsychotic medications. Here, we investigate the effects of administration of the antipsychotic haloperidol and NMDAR agonist d-serine on function and expression of three proteins that play significant roles in SCZ: nitric oxide synthase 1 adaptor protein (NOS1AP), dopamine D2 (D2) receptor, and disrupted in schizophrenia 1 (DISC1). We administered haloperidol or d-serine to male and female Sprague Dawley rats via intraperitoneal injection for 12 days and subsequently examined cortical expression of NOS1AP, D2 receptor, and DISC1. We found sex-specific effects of haloperidol and d-serine treatment on the expression of these proteins. Haloperidol significantly reduced expression of D2 receptor in male, but not female, rats. Conversely, d-serine reduced expression of NOS1AP in male rats and did not affect D2 receptor expression. d-serine treatment also reduced expression of DISC1 in male rats and increased DISC1 expression in female rats. As NOS1AP is overexpressed in the cortex of patients with SCZ and negatively regulates NMDAR signaling, we subsequently examined whether treatment with antipsychotics or NMDAR agonists can reverse the detrimental effects of NOS1AP overexpression in vitro as previously reported by our group. NOS1AP overexpression promotes reduced dendrite branching in vitro, and as such, we treated cortical neurons overexpressing NOS1AP with different antipsychotics (haloperidol, clozapine, fluphenazine) or d-serine for 24 h and determined the effects of these drugs on NOS1AP expression and dendrite branching. While antipsychotics did not affect NOS1AP protein expression or dendrite branching in vitro, d-serine reduced NOS1AP expression and rescued NOS1AP-mediated reductions in dendrite branching. Taken together, our data suggest that d-serine influences the function and expression of NOS1AP, D2 receptor, and DISC1 in a sex-specific manner and reverses the effects of NOS1AP overexpression on dendrite morphology.

Effectiveness of Prescription-Based CNS Stimulants on Hospitalization in Patients With Schizophrenia: A Nation-Wide Register Study

OBJECTIVE

Negative symptoms and cognitive deficits are main features of schizophrenia but with limited treatment options. Earlier studies have suggested that central nervous system (CNS) stimulants have a small effect on these domains, but with inconclusive results. As the first study to date, we aimed to investigate whether CNS stimulants improve naturalistic outcomes (psychiatric admissions and antipsychotic use) in patients with schizophrenia.

METHODS

By using extensive health registers all patients with schizophrenia and their use of CNS stimulants in Denmark were identified. Two models were used to investigate the effectiveness of CNS stimulants in patients with schizophrenia between 1995 and 2014; a mirror-image model with 605 individuals, using paired t tests and Wilcoxon signed rank tests, and a follow-up study with 789 individuals, using a conditional risk-set model.

RESULTS

CNS stimulants use was associated with a reduction in number of psychiatric admissions from 3.43 (95% CI = 2.86 to 4.01) to 2.62 (95% CI = 1.99 to 3.25) (P = .009), with a more pronounced reduction for women (mean difference: -1.37, 95% CI = -2.34 to -0.40, P = .006). Psychiatric bed-days were reduced by 40 (95% CI = 24.5 to 55.6, P < .001) for individuals with at least 1 admission before CNS stimulant use. In addition, the total amount of antipsychotic use (Defined Daily Dose [DDD]) was reduced (P = .001). The Hazard rate ratio in psychiatric admissions between women taking CNS stimulants compared to women not taking CNS stimulants was 0.77 (95% CI = 0.67 to 0.88).

CONCLUSION

CNS stimulants may have clinical potentials for improving functional outcomes in patients with schizophrenia and randomized clinical studies evaluating this topic are warranted.

Ascorbic Acid to Manage Psychiatric Disorders

Ascorbate has critical roles in the central nervous system (CNS); it is a neuromodulator of glutamatergic, cholinergic, dopaminergic, and γ-aminobutyric acid (GABA)-ergic neurotransmission, provides support and structure to neurons, and participates in processes such as differentiation, maturation, and survival of neurons. Over the past decade, antioxidant properties of ascorbate have been extensively characterized and now it is known that this compound is highly concentrated in the brain and neuroendocrine tissues. All this information raised the hypothesis that ascorbate may be involved in neurological disorders. Indeed, the biological mechanisms of ascorbate in health and disease and its involvement in homeostasis of the CNS have been the subject of extensive research. In particular, evidence for an association of this vitamin with schizophrenia, major depressive disorder, and bipolar disorder has been provided. Considering that conventional pharmacotherapy for the treatment of these neuropathologies has important limitations, this review aims to explore basic and human studies that implicate ascorbic acid as a potential therapeutic strategy. Possible mechanisms involved in the beneficial effects of ascorbic acid for the management of psychiatric disorders are also discussed.

The Effects of Age, from Young to Middle Adulthood, and Gender on Resting State Functional Connectivity of the Dopaminergic Midbrain

Dysfunction of the dopaminergic ventral tegmental area (VTA) and substantia nigra pars compacta (SNc) is implicated in psychiatric disorders including attention-deficit/ hyperactivity disorder (ADHD), addiction, schizophrenia and movement disorders such as Parkinson's disease (PD). Although the prevalence of these disorders varies by age and sex, the underlying neural mechanism is not well understood. The objective of this study was to delineate the distinct resting state functional connectivity (rsFC) of the VTA and SNc and examine the effects of age, from young to middle-adulthood, and sex on the rsFC of these two dopaminergic structures in a data set of 250 healthy adults (18-49 years of age, 104 men). Using blood oxygenation level dependent (BOLD) signals, we correlated the time course of the VTA and SNc to the time courses of all other brain voxels. At a corrected threshold, paired t-test showed stronger VTA connectivity to bilateral angular gyrus and superior/middle and orbital frontal regions and stronger SNc connectivity to the insula, thalamus, parahippocampal gyrus (PHG) and amygdala. Compared to women, men showed a stronger VTA/SNc connectivity to the left posterior orbital gyrus. In linear regressions, men but not women showed age-related changes in VTA/SNc connectivity to a number of cortical and cerebellar regions. Supporting shared but also distinct cerebral rsFC of the VTA and SNc and gender differences in age-related changes from young and middle adulthood in VTA/SNc connectivity, these new findings help advance our understanding of the neural bases of many neuropsychiatric illnesses that implicate the dopaminergic systems.

Recent Advances in Synthesis and Biomedical Applications of Two-Dimensional Transition Metal Dichalcogenide Nanosheets

During recent decades, a giant leap in the development of nanotechnology has been witnessed. Numerous nanomaterials with different dimensions and unprecedented features have been developed and provided unimaginably wide scope to solve the challenging problems in biomedicine, such as cancer diagnosis and therapy. Recently, two-dimensional (2D) transition metal dichalcogenide (TMDC) nanosheets (NSs), including MoS₂ , WS₂ , and etc., have emerged as novel inorganic graphene analogues and attracted tremendous attention due to their unique structures and distinctive properties, and opened up great opportunities for biomedical applications, including ultrasensitive biosensing, biological imaging, drug delivery, cancer therapy, and antibacterial treatment. A comprehensive overview of different synthetic methods of ultrathin 2D TMDC NSs and their state-of-the-art biomedical applications, especially those that have appeared in the past few years, is presented. At the end of this review, the future opportunities and challenges for 2D TMDC NSs in biomedicine are also discussed.

Relationship between plasma homovanillic acid and outcome in patients with psychosis spectrum disorders

BACKGROUND

Psychosis spectrum disorders, especially schizophrenia, have been linked to disturbed dopaminergic activity in the brain. Plasma homovanillic acid (pHVA) levels partly represent dopaminergic metabolism in the central nervous system. In the present study associations between (changes in) pHVA levels, symptom severity and symptomatic improvement in patients with psychoses were investigated.

METHODS

From a total of 80 patients, 58 fulfilled all inclusion criteria and their symptom profile and severity were assessed by means of the Comprehensive Assessment of Symptoms and History (CASH), the Positive and Negative Syndrome Scale (PANSS) and the Clinical Global Impression Scale for Severity and Improvement (CGI-S/CGI-I) at baseline and after 6 weeks of antipsychotic treatment. After inclusion, all patients were prescribed first- or second-generation antipsychotics by their treating psychiatrist. A total of 12 patients had first-episode psychosis (FEP). At both time points, pHVA levels were measured. Subsequently, pHVA levels were compared with an age-matched control sample and changes in pHVA levels (ΔpHVA) after treatment were associated with clinical parameters.

RESULTS

Before analyses, data were scrutinized for possible confounders, particularly gender, smoking, medication status (including antipsychotic class), and recent drug use. The pHVA levels in patients were not different from those in controls. Treatment resulted in a significant decrease of all parameters. Symptomatic improvement as well as ΔpHVA was most pronounced in FEP patients.

CONCLUSION

These findings show that patients with FEP have a more favourable outcome than non-FEP patients and that greater ΔpHVA also suggests that FEP patients still have the capacity to adjust dopaminergic neurotransmission.

Likelihood of mechanistic roles for dopaminergic, serotonergic and glutamatergic receptors in tardive dyskinesia: A comparison of genetic variants in two independent patient populations

Objectives:

An established theory for the pathogenesis of tardive dyskinesia is disturbed dopaminergic receptor sensitivity and/or dopaminergic intracellular signaling. We examined associations between genetic variants of neurotransmitter receptors and tardive dyskinesia.

Methods:

We assessed tardive dyskinesia in Caucasian psychiatric inpatients from Siberia (N = 431) and a long-stay population from the Netherlands (N = 168). These patients were genotyped for 43 tag single nucleotide polymorphisms in five neurotransmitter receptor genes, and the results for the two populations were compared.

Results:

Several significant associations with tardive dyskinesia were identified, but only GRIN2A (rs1345423) was found in both patient populations. This lack of agreement was probably due to the small effect size of the associations, the multiple testing and the small sample size of the Dutch patient population. After reviewing the literature, we propose that the constitutive stimulatory activity of serotonergic type 2 receptors may be relevant.

Conclusions:

Inactivity of the serotonergic, type 2C receptor or blockade of these receptors by atypical antipsychotic drugs may decrease the vulnerability to develop tardive dyskinesia.

Dopamine-prolactin pathway potentially contributes to the schizophrenia and type 2 diabetes comorbidity

Schizophrenia (SCZ) and type 2 diabetes (T2D) are clinically associated, and common knowledge attributes this association to side effects of antipsychotic treatment. However, even drug-naive patients with SCZ are at increased risk for T2D. Dopamine dysfunction has a central role in SCZ. It is well-known that dopamine constitutively inhibits prolactin (PRL) secretion via the dopamine receptor 2 (DR2D). If dopamine is increased or if dopamine receptors hyperfunction, PRL may be reduced. During the first SCZ episode, low PRL levels are associated with worse symptoms. PRL is essential in human and social bonding, as well as it is implicated in glucose homeostasis. Dopamine dysfunction, beyond contributing to SCZ symptoms, may lead to altered appetite and T2D. To our knowledge, there are no studies of the genetics of the SCZ-T2D comorbidity focusing jointly on the dopamine and PRL pathway in the attempt to capture molecular heterogeneity correlated to possible disease manifestation heterogeneity. In this dopamine-PRL pathway-focused-hypothesis-driven review on the association of SCZ with T2D, we report a specific revision of what it is known about PRL and dopamine in relation to what we theorize is one of the missing links between the two disorders. We suggest that new studies are necessary to establish the genetic role of PRL and dopamine pathway in SCZ-T2D comorbidity.

Focus on psychosis

The concept of psychosis has been shaped by traditions in the concepts of mental disorders during the last 170 years. The term "psychosis" still lacks a unified definition, but denotes a clinical construct composed of several symptoms. Delusions, hallucinations, and thought disorders are the core clinical features. The search for a common denominator of psychotic symptoms points toward combinations of neuropsychological mechanisms resulting in reality distortion. To advance the elucidation of the causes and the pathophysiology of the symptoms of psychosis, a deconstruction of the term into its component symptoms is therefore warranted. Current research is dealing with the delineation from "normality", the genetic underpinnings, and the causes and pathophysiology of the symptoms of psychosis.

Neuromodulation of excitatory synaptogenesis in striatal development

Dopamine is released in the striatum during development and impacts the activity of Protein Kinase A (PKA) in striatal spiny projection neurons (SPNs). We examined whether dopaminergic neuromodulation regulates activity-dependent glutamatergic synapse formation in the developing striatum. Systemic in vivo treatment with Gα_s-coupled G-protein receptors (GPCRs) agonists enhanced excitatory synapses on direct pathway striatal spiny projection neurons (dSPNs), whereas rapid production of excitatory synapses on indirect pathway neurons (iSPNs) required the activation of Gα_s GPCRs in SPNs of both pathways. Nevertheless, in vitro Gα_s activation was sufficient to enhance spinogenesis induced by glutamate photolysis in both dSPNs and iSPNs, suggesting that iSPNs in intact neural circuits have additional requirements for rapid synaptic development. We evaluated the in vivo effects of enhanced glutamate release from corticostriatal axons and postsynaptic PKA and discovered a mechanism of developmental plasticity wherein rapid synaptogenesis is promoted by the coordinated actions of glutamate and postsynaptic Gα_s-coupled receptors.

DOI:http://dx.doi.org/10.7554/eLife.10111.001

The brain is composed of intricate circuits of connected neurons that communicate via a combination of electrical and chemical signals. Some signals (referred to as excitatory signals) increase the probability that the neuron receiving the chemical message will produce an electrical impulse. On the other hand, inhibitory messages decrease the likelihood of this activity. Both of these kinds of signals are fast, and act over milliseconds. There is also a diverse set of slower signals, referred to as neuromodulation, which regulates the faster signals. A signaling chemical called dopamine is involved in neuromodulation and is essential for rewarding behavior and complex motor actions. The importance of dopamine is clear from the profound lack of movement seen in individuals with Parkinson’s disease, which is caused by the death of dopamine producing brain cells.

Many nerve endings from dopamine-releasing neurons connect to a part of the brain’s reward system called the striatum. The neurons in this region are organized into two pathways that have opposing impacts on behavior. Dopamine activates different kinds of receptors called “G protein-coupled dopamine receptors” on neurons from each pathway. This allows dopamine to alter the activity of a protein called Protein Kinase A (or PKA) and alter the signaling state of these neurons.

The impact of dopamine on neural circuits in adults has been extensively studied. However it was unknown whether dopamine might influence how neural circuits are wired during brain development. Because the nerve endings from dopamine-releasing neurons reach the striatum before most excitatory connections between the neurons are formed, dopamine stands to influence the development of connections in the striatum.

Kozorovitskiy et al. have now investigated the role of neuromodulation in brain development in young mice. This involved measuring the formation of excitatory connections or synapses and the electrical activity of different striatal neurons during the maturation of brain circuits that occurs after birth. This analysis revealed that turning on dopamine receptors that increase PKA activity rapidly enhances the number of excitatory synapses on the neurons that express this receptor.

Kozorovitskiy et al. then used a variety of approaches to investigate whether there is cooperation between G protein-coupled receptors, PKA activity and a signaling molecule called glutamate in striatal development. This revealed a more general mechanism by which the activation of G-protein-coupled receptors interacts with glutamate (the primary excitatory signal sent between neurons) in order to produce new synapses. These results reveal a previously unknown role for neuromodulation in “wiring up” the brain and open the possibility of new therapies to treat neurodevelopmental and neurodegenerative disorders.

DOI:http://dx.doi.org/10.7554/eLife.10111.002

MK-801 and amphetamine result in dissociable profiles of cognitive impairment in a rodent paired associates learning task with relevance for schizophrenia

RATIONALE

Paired associates learning (PAL) has been suggested to be predictive of functional outcomes in first episode psychosis and of conversion from mild cognitive impairment to Alzheimer's disease. An automated touch screen-based rodent PAL (rPAL) task has been developed and is sensitive to manipulations of the dopaminergic and glutamatergic system. Accordingly, rPAL when used with pharmacological models of schizophrenia, like NMDA receptor blockade with MK-801 or dopaminergic stimulation with amphetamine, may have utility as a translational model of cognitive impairment in schizophrenia.

OBJECTIVE

The purpose of this study was to determine if amphetamine- and MK-801-induced impairment represent distinct models of cognitive impairment by testing their sensitivity to common antipsychotics and determine the relative contributions of D1 versus D2 receptors on performance of PAL.

METHOD

Rats were trained in rPAL and were then treated with MK-801, amphetamine, risperidone, haloperidol, quinpirole, SK-82958, or SCH-23390 alone and in combination.

RESULTS

While both amphetamine and MK-801 caused clear impairments in accuracy, MK-801 induced a profound "perseverative" type behavior that was more pronounced when compared to amphetamine. Moreover, amphetamine-induced impairments, but not the effects of MK-801, could be reversed by antipsychotics as well as the D1 receptor antagonist SCH-23390, suggesting a role for both the D1 and D2 receptor in the amphetamine impairment model.

CONCLUSIONS

These data suggest that amphetamine and MK-801 represent dissociable models of impairment in PAL, dependent on different underlying neurobiology. The ability to distinguish dopaminergic versus glutamatergic effects on performance in rPAL makes it a unique and useful tool in the modeling of cognitive impairments in schizophrenia.

Local and Global Resting State Activity in the Noradrenergic and Dopaminergic Pathway Modulated by Reboxetine and Amisulpride in Healthy Subjects

BACKGROUND

Various psychiatric populations are currently investigated with resting state fMRI, with the aim of individualizing diagnostics and treatment options and improving treatment outcomes. Many of these studies are conducted in large naturalistic samples, providing rich insights regarding disease-related neural alterations, but with the common psychopharmacological medication limiting interpretations of the results. We therefore investigated the effects of common noradrenergic and anti-dopaminergic medications on local and global resting state activity (rs-activity) in healthy volunteers to further the understanding of the respective effects independent from disease-related alterations.

METHODS

Within a randomized, double-blind, placebo-controlled crossover design, we investigated 19 healthy male subjects by resting state fMRI after the intake of reboxetine (4 mg/d), amisulpride (200mg/d), and placebo for 7 days each. Treatment-related differences in local and global rs-activity were measured by the fractional amplitude of low frequency fluctuations (fALFF) and resting state functional connectivity (rs-FC).

RESULTS

fALFF revealed alterations of local rs-activity within regions of the core noradrenergic pathway, including the locus coeruleus under reboxetine, correlated with its plasma levels. Moreover, reboxetine led to increased rs-FC between regions within this pathway, i.e. the locus coeruleus, tectum, thalamus, and amygdala. Amisulpride modulated local rs-activity of regions within the dopaminergic pathway, with the altered signal in the putamen correlating with amisulpride plasma levels. Correspondingly, amisulpride increased rs-FC between regions of the dopaminergic pathway comprising the substantia nigra and putamen.

CONCLUSION

Our data provide evidence of how psychopharmacological agents alter local and global rs-activity within the respective neuroanatomical pathways in healthy subjects, which may help with interpreting data in psychiatric populations.