The role of norepinephrine in the pathophysiology of schizophrenia

Dysbindin-1 Mutation Alters Prefrontal Cortex Extracellular Glutamate and Dopamine In Vivo

Elevated risk for schizophrenia is associated with a variation in the DTNBP1 gene encoding dysbindin-1, which may underpin cognitive impairments in this prevalent neuropsychiatric disorder. The cognitive symptoms of schizophrenia involve anomalies in glutamate and dopamine signaling, particularly within the prefrontal cortex (PFC). Indeed, mice with Dtnbp1 mutations exhibit spatial and working memory deficits that are associated with deficits in glutamate release and NMDA receptor function as determined by slice electrophysiology. The present study extended the results from ex vivo approaches by examining how the Dtnbp1 mutation impacts high K+- and NMDA receptor-evoked glutamate release within the PFC using in vivo microdialysis procedures. Dntbp1 mutant mice are also reported to exhibit blunted K+-evoked dopamine release within the PFC. Thus, we examined also K+- and NMDA-evoked dopamine release within this region. Perfusion of high-concentration K+ or NMDA solutions increased the PFC levels of both dopamine and glutamate in wild-type (WT) but not in Dtnbp1 mutants (MUT), whereas mice heterozygous for the Dtnbp1 mutation (HET) exhibited blunted K+-evoked dopamine release. No net-flux microdialysis procedures confirmed elevated basal extracellular content of both glutamate and dopamine within the PFC of HET and MUT mice. These in vivo microdialysis results corroborate prior indications that Dtnbp1 mutations perturb evoked dopamine and glutamate release within the PFC, provide in vivo evidence for impaired NMDA receptor function within the PFC, and suggest that these neurochemical anomalies may be related to abnormally elevated basal neurotransmitter content.

Brain metabolic profiling of schizophrenia: a path towards a better understanding of the neuropathogenesis of psychosis

Schizophrenia (SCZ) is a complex psychotic syndrome whose pathogenesis involves countless protagonists, none of which, to date, can fully explain how this disorder develops. In this narrative review, an overview of the biochemical impairment is offered according to several perspectives. Indeed, the metabolic framework behind SCZ dopaminergic hypotheses, glutamate - gamma-amynobutyric acid dysregulation, norepinephrine and serotonin, calcium channel dysfunction is addressed together with the energetic impairment, involving glucose and lipids in SCZ etiopathogenesis, in order to highlight the multilevel pathways affected in this neuropsychiatric disorder. Furthermore, neuroinflammation is analyzed, by virtue of its important role, widely investigated in recent years, in neurodegeneration. Tracing the neurotransmitter activity at the brain level by assessing the metabolic network behind the abovementioned molecules puts into light as unavoidable the need for future studies to adopt an integrate approach to address SCZ pathological and clinical picture. The combination of all these factors, essential in acquiring an overview on the complexity of SCZ pathophysiology represents a crucial step in the development of a more targeted management of SCZ patients.

Evaluation of the Glymphatic System in Schizophrenia Spectrum Disorder Using Proton Magnetic Resonance Spectroscopy Measurement of Brain Macromolecule and Diffusion Tensor Image Analysis Along the Perivascular Space Index

BACKGROUND AND HYPOTHESIS

The glymphatic system (GS), a brain waste clearance pathway, is disrupted in various neurodegenerative and vascular diseases. As schizophrenia shares clinical characteristics with these conditions, we hypothesized GS disruptions in patients with schizophrenia spectrum disorder (SCZ-SD), reflected in increased brain macromolecule (MM) and decreased diffusion-tensor-image-analysis along the perivascular space (DTI-ALPS) index.

STUDY DESIGN

Forty-seven healthy controls (HCs) and 103 patients with SCZ-SD were studied. Data included 135 proton magnetic resonance spectroscopy (1H-MRS) sets, 96 DTI sets, with 79 participants contributing both. MM levels were quantified in the dorsal-anterior cingulate cortex (dACC), dorsolateral prefrontal cortex, and dorsal caudate (point resolved spectroscopy, echo-time = 35ms). Diffusivities in the projection and association fibers near the lateral ventricle were measured to calculate DTI-ALPS indices. General linear models were performed, adjusting for age, sex, and smoking. Correlation analyses examined relationships with age, illness duration, and symptoms severity.

STUDY RESULTS

MM levels were not different between patients and HCs. However, left, right, and bilateral DTI-ALPS indices were lower in patients compared with HCs (P < .001). In HCs, age was positively correlated with dACC MM and negatively correlated with left, right, and bilateral DTI-ALPS indices (P < .001). In patients, illness duration was positively correlated with dACC MM and negatively correlated with the right DTI-ALPS index (P < .05). In the entire population, dACC MM and DTI-ALPS indices showed an inverse correlation (P < .01).

CONCLUSIONS

Our results suggest potential disruptions in the GS of patients with SCZ-SD. Improving brain's waste clearance may offer a potential therapeutic approach for patients with SCZ-SD.

Altered intrinsic neural activity and its molecular analyses in first-episode schizophrenia with auditory verbal hallucinations

Background

Auditory verbal hallucinations (AVHs) are one of the signature positive symptoms of schizophrenia, affecting a substantial portion of patients with schizophrenia. These hallucinations seriously impact the lives of patients, resulting in a substantial social burden. Recent studies have shown a significant correlation between abnormal local brain activity and the neurobiological mechanisms of AVHs. However, it is not fully clear whether altered intrinsic brain activity in schizophrenia patients with AVHs is correlated with specific neurotransmitter systems.

Methods

We included 50 first-episode, drug-naïve schizophrenia patients with AVHs, 50 patients without AVHs (NAVHs), and 50 age- and sex-matched healthy controls (HCs). The amplitude of low-frequency fluctuation (ALFF) was utilized to explore the altered intrinsic brain activity in the AVH group. Subsequently, we spatially correlated the altered ALFF with neurotransmitter maps using JuSpace.

Results

In our study, compared to HCs, the AVH group exhibited significantly reduced ALFF in multiple brain regions, mainly including the left precuneus, bilateral supplementary motor areas, bilateral paracentral lobules, bilateral precentral gyri, and bilateral postcentral gyri. The NAVH group showed significantly reduced ALFF in the left inferior occipital gyrus, left calcarine gyrus, and left lingual gyrus compared to HCs. Furthermore, the AVH group showed higher ALFF in the right inferior frontal gyrus compared to the NAVH group. Additionally, these ALFF alterations in the AVH group were closely related to three neurotransmitters, including dopamine, serotonin and norepinephrine.

Conclusion

We link neurotransmitters to abnormal intrinsic brain activity in first-episode, drug-naïve schizophrenia patients with AVHs, contributing to a comprehensive understanding of the pathophysiological processes and treatment pathways underlying AVHs.

Neural circuit-selective, multiplexed pharmacological targeting of prefrontal cortex-projecting locus coeruleus neurons drives antinociception

Selective manipulation of neural circuits using optogenetics and chemogenetics holds great translational potential but requires genetic access to neurons. Here, we demonstrate a general framework for identifying genetic tool-independent, pharmacological strategies for neural circuit-selective modulation. We developed an economically accessible calcium imaging-based approach for large-scale pharmacological scans of endogenous receptor-mediated neural activity. As a testbed for this approach, we used the mouse locus coeruleus due to the combination of its widespread, modular efferent neural circuitry and its wide variety of endogenously expressed GPCRs. Using machine learning-based action potential deconvolution and retrograde tracing, we identified an agonist cocktail that selectively inhibits medial prefrontal cortex-projecting locus coeruleus neurons. In vivo, this cocktail produces synergistic antinociception, consistent with selective pharmacological blunting of this neural circuit. This framework has broad utility for selective targeting of other neural circuits under different physiological and pathological states, facilitating non-genetic translational applications arising from cell type-selective discoveries.

Glymphatic System Dysfunction Underlying Schizophrenia Is Associated With Cognitive Impairment

BACKGROUND AND HYPOTHESIS

Despite the well-documented structural and functional brain changes in schizophrenia, the potential role of glymphatic dysfunction remains largely unexplored. This study investigates the glymphatic system's function in schizophrenia, utilizing diffusion tensor imaging (DTI) to analyze water diffusion along the perivascular space (ALPS), and examines its correlation with clinical symptoms.

STUDY DESIGN

A cohort consisting of 43 people with schizophrenia and 108 healthy controls was examined. We quantified water diffusion metrics along the x-, y-, and z-axis in both projection and association fibers to derive the DTI-ALPS index, a proxy for glymphatic activity. The differences in the ALPS index between groups were analyzed using a 2-way ANCOVA controlling for age and sex, while partial correlations assessed the association between the ALPS index and clinical variables.

STUDY RESULTS

People with schizophrenia showed a significantly reduced DTI-ALPS index across the whole brain and within both hemispheres (F = 9.001, P = .011; F = 10.024, P = .011; F = 5.927, P = .044; false discovery rate corrected), indicating potential glymphatic dysfunction in schizophrenia. The group by cognitive performance interaction effects on the ALPS index were not observed. Moreover, a lower ALPS index was associated with poorer cognitive performance on specific neuropsychological tests in people with schizophrenia.

CONCLUSION

Our study highlights a lower ALPS index in schizophrenia, correlated with more pronounced cognitive impairments. This suggests that glymphatic dysfunction may contribute to the pathophysiology of schizophrenia, offering new insights into its underlying mechanisms.

Diverging functional connectivity timescales: Capturing distinct aspects of cognitive performance in early psychosis

BACKGROUND

Psychosis spectrum disorders (PSDs) are marked by cognitive impairments, the neurobiological correlates of which remain poorly understood. Here, we investigate the entropy of time-varying functional connectivity (TVFC) patterns from resting-state functional magnetic resonance imaging (rs-fMRI) as potential biomarker for cognitive performance in PSDs. By combining our results with multimodal reference data, we hope to generate new insights into the mechanisms underlying cognitive dysfunction in PSDs. We hypothesized that low-entropy TVFC patterns (LEN) would be more behaviorally informative than high-entropy TVFC patterns (HEN), especially for tasks that require extensive integration across diverse cognitive subdomains.

METHODS

rs-fMRI and behavioral data from 97 patients in the early phases of psychosis and 53 controls were analyzed. Positron emission tomography (PET) and magnetoencephalography (MEG) data were taken from a public repository (Hansen et al., 2022). Multivariate analyses were conducted to examine relationships between TVFC patterns at multiple spatial scales and cognitive performance in patients.

RESULTS

Compared to HEN, LEN explained significantly more cognitive variance on average in PSD patients, driven by superior encoding of information on psychometrically more integrated tasks. HEN better captured information in specific subdomains of executive functioning. Nodal HEN-LEN transitions were spatially aligned with neurobiological gradients reflecting monoaminergic transporter densities and MEG beta-power. Exploratory analyses revealed a close statistical relationship between LEN and positive symptom severity in patients.

CONCLUSION

Our entropy-based analysis of TVFC patterns dissociates distinct aspects of cognition in PSDs. By linking topographies of neurotransmission and oscillatory dynamics with cognitive performance, it enhances our understanding of the mechanisms underlying cognitive deficits in PSDs.

Diverging functional connectivity timescales: Capturing distinct aspects of cognitive performance in early psychosis

Background

Psychosis spectrum disorders (PSDs) are marked by cognitive impairments, the neurobiological correlates of which remain poorly understood. Here, we investigate the entropy of time-varying functional connectivity (TVFC) patterns from resting-state fMRI (rfMRI) as potential biomarker for cognitive performance in PSDs. By combining our results with multimodal reference data, we hope to generate new insights into the mechanisms underlying cognitive dysfunction in PSDs. We hypothesized that low-entropy TVFC patterns (LEN) would be more behaviorally informative than high-entropy TVFC patterns (HEN), especially for tasks that require extensive integration across diverse cognitive subdomains.

Methods

rfMRI and behavioral data from 97 patients in the early phases of psychosis and 53 controls were analyzed. Positron-Emission Tomography (PET) and magnetoencephalography (MEG) data were taken from a public repository (Hansen et al., 2022). Multivariate analyses were conducted to examine relationships between TVFC patterns at multiple spatial scales and cognitive performance in patients.

Results

Compared to HEN, LEN explained significantly more cognitive variance on average in PSD patients, driven by superior encoding of information on psychometrically more integrated tasks. HEN better captured information in specific subdomains of executive functioning. Nodal HEN-LEN transitions were spatially aligned with neurobiological gradients reflecting monoaminergic transporter densities and MEG beta power. Exploratory analyses revealed a close statistical relationship between LEN and positive PSD symptoms.

Conclusion

Our entropy-based analysis of TVFC patterns dissociates distinct aspects of cognition in PSDs. By linking topographies of neurotransmission and oscillatory dynamics with cognitive performance, it enhances our understanding of the mechanisms underlying cognitive deficits in PSDs.

CRediT Authorship Contribution Statement

Fabian Hirsch: Conceptualization, Methodology, Software, Formal analysis, Writing - Original Draft, Writing - Review & Editing, Visualization; Ângelo Bumanglag: Methodology, Software, Formal analysis, Writing - Review & Editing; Yifei Zhang: Methodology, Software, Formal analysis, Writing - Review & Editing; Afra Wohlschlaeger: Methodology, Writing - Review & Editing, Supervision, Project administration.

Neuromelanin-sensitive magnetic resonance imaging: Possibilities and promises as an imaging biomarker for Parkinson's disease

Parkinson's disease (PD) is an age-related progressive neurodegenerative disorder characterized by both motor and non-motor symptoms resulting from the death of dopaminergic neurons in the substantia nigra pars compacta (SNpc) and noradrenergic neurons in the locus coeruleus (LC). The current diagnosis of PD primarily relies on motor symptoms, often leading to diagnoses in advanced stages, where a significant portion of SNpc dopamine neurons has already succumbed. Therefore, the identification of imaging biomarkers for early-stage PD diagnosis and disease progression monitoring is imperative. Recent studies propose that neuromelanin-sensitive magnetic resonance imaging (NM-MRI) holds promise as an imaging biomarker. In this review, we summarize the latest findings concerning NM-MRI characteristics at various stages in patients with PD and those with atypical parkinsonism. In conclusion, alterations in neuromelanin within the LC are associated with non-motor symptoms and prove to be a reliable imaging biomarker in the prodromal phase of PD. Furthermore, NM-MRI demonstrates efficacy in differentiating progressive supranuclear palsy (PSP) from PD and multiple system atrophy with predominant parkinsonism. The spatial patterns of changes in the SNpc can be indicative of PD progression and aid in distinguishing between PSP and synucleinopathies. We recommend that patients with PD and individuals at risk for PD undergo regular NM-MRI examinations. This technology holds the potential for widespread use in PD diagnosis.

New Therapeutic Targets and Drugs for Schizophrenia Beyond Dopamine D2 Receptor Antagonists

Schizophrenia is a disease with a complex pathological mechanism that is influenced by multiple genes. The study of its pathogenesis is dominated by the dopamine hypothesis, as well as other hypotheses such as the 5-hydroxytryptamine hypothesis, glutamate hypothesis, immune-inflammatory hypothesis, gene expression abnormality hypothesis, and neurodevelopmental abnormality hypothesis. The first generation of antipsychotics was developed based on dopaminergic receptor antagonism, which blocks dopamine D2 receptors in the brain to exert antipsychotic effects. The second generation of antipsychotics acts by dual blockade of 5-hydroxytryptamine and dopamine receptors. From the third generation of antipsychotics onwards, the therapeutic targets for antipsychotic schizophrenia expanded beyond D2 receptor blockade to explore D2 receptor partial agonism and the antipsychotic effects of new targets such as D3, 5-HT1A, 5-HT7, and mGlu2/3 receptors. The main advantages of the second and third generation antipsychotics over first-generation antipsychotics are the reduction of side effects and the improvement of negative symptoms, and even though third-generation antipsychotics do not directly block D2 receptors, the modulation of the dopamine transmitter system is still an important part of their antipsychotic process. According to recent research, several receptors, including 5-hydroxytryptamine, glutamate, γ-aminobutyric acid, acetylcholine receptors and norepinephrine, play a role in the development of schizophrenia. Therefore, the focus of developing new antipsychotic drugs has shifted towards agonism or inhibition of these receptors. Specifically, the development of NMDARs stimulants, GABA receptor agonists, mGlu receptor modulators, cholinergic receptor modulators, 5-HT2C receptor agonists and alpha-2 receptor modulators has become the main direction. Animal experiments have confirmed the antipsychotic effects of these drugs, but their pharmacokinetics and clinical applicability still require further exploration. Research on alternative targets for antipsychotic drugs, beyond the dopamine D2 receptor, has expanded the potential treatment options for schizophrenia and gives an important way to address the challenge of refractory schizophrenia. This article aims to provide a comprehensive overview of the research on therapeutic targets and medications for schizophrenia, offering valuable insights for both treatment and further research in this field.

Large nesting expression in deer mice remains stable under conditions of visual deprivation despite heightened limbic involvement: Perspectives on compulsive-like behavior

Visual stimuli and limbic activation varyingly influence obsessive-compulsive symptom expression and so impact treatment outcomes. Some symptom phenotypes, for example, covert repugnant thoughts, are likely less sensitive to sensory stimuli compared to symptoms with an extrinsic focus, that is, symptoms related to contamination, safety, and "just-right-perceptions." Toward an improved understanding of the neurocognitive underpinnings of obsessive-compulsive psychobiology, work in naturalistic animal model systems is useful. Here, we explored the impact of visual feedback and limbic processes on 24 normal (NNB) and large (LNB) nesting deer mice, respectively (as far as possible, equally distributed between sexes). Briefly, after behavioral classification into either the NNB or LNB cohorts, mice of each cohort were separated into two groups each and assessed for nesting expression under either standard light conditions or conditions of complete visual deprivation (VD). Nesting outcomes were assessed in terms of size and neatness. After nesting assessment completion, mice were euthanized, and samples of frontal-cortical and hippocampal tissues were collected to determine serotonin and noradrenaline concentrations. Our results show that LNB, as opposed to NNB, represents an inflexible and excessive behavioral phenotype that is not dependent on visually guided action-outcome processing, and that it associates with increased frontal-cortical and hippocampal noradrenaline concentrations, irrespective of lighting condition. Collectively, the current results are informing of the neurocognitive underpinnings of nesting behavior. It also provides a valuable foundation for continued investigations into the noradrenergic mechanisms that may influence the development and promulgation of excessive, rigid, and inflexible behaviors.

Associating Multimodal Neuroimaging Abnormalities With the Transcriptome and Neurotransmitter Signatures in Schizophrenia

BACKGROUND AND HYPOTHESIS

Schizophrenia is a multidimensional disease. This study proposes a new research framework that combines multimodal meta-analysis and genetic/molecular architecture to solve the consistency in neuroimaging biomarkers of schizophrenia and whether these link to molecular genetics.

STUDY DESIGN

We systematically searched Web of Science, PubMed, and BrainMap for the amplitude of low-frequency fluctuations (ALFF) or fractional ALFF, regional homogeneity, regional cerebral blood flow, and voxel-based morphometry analysis studies investigating schizophrenia. The pooled-modality, single-modality, and illness duration-dependent meta-analyses were performed using the activation likelihood estimation algorithm. Subsequently, Spearman correlation and partial least squares regression analyses were conducted to assess the relationship between identified reliable convergent patterns of multimodality and neurotransmitter/transcriptome, using prior molecular imaging and brain-wide gene expression.

STUDY RESULTS

In total, 203 experiments comprising 10 613 patients and 10 461 healthy controls were included. Multimodal meta-analysis showed that brain regions of significant convergence in schizophrenia were mainly distributed in the frontotemporal cortex, anterior cingulate cortex, insula, thalamus, striatum, and hippocampus. Interestingly, the analyses of illness-duration subgroups identified aberrant functional and structural evolutionary patterns: Lines from the striatum to the cortical core networks to extensive cortical and subcortical regions. Subsequently, we found that these robust multimodal neuroimaging abnormalities were associated with multiple neurobiological abnormalities, such as dopaminergic, glutamatergic, serotonergic, and GABAergic systems.

CONCLUSIONS

This work links transcriptome/neurotransmitters with reliable structural and functional signatures of brain abnormalities underlying disease effects in schizophrenia, which provides novel insight into the understanding of schizophrenia pathophysiology and targeted treatments.

Dysregulated noradrenergic response is associated with symptom severity in individuals with schizophrenia

Introduction

The locus coeruleus-noradrenaline (LC-NA) system is involved in a wide range of cognitive functions and may be altered in schizophrenia. A non-invasive method to indirectly measure LC activity is task-evoked pupillary response. Individuals with schizophrenia present reduced pupil dilation compared to healthy subjects, particularly when task demand increases. However, the extent to which alteration in LC activity contributes to schizophrenia symptomatology remains largely unexplored. We aimed to investigate the association between symptomatology, cognition, and noradrenergic response in individuals with schizophrenia.

Methods

We assessed task-evoked pupil dilation during a pro- and antisaccade task in 23 individuals with schizophrenia and 28 healthy subjects.

Results

Both groups showed similar preparatory pupil dilation during prosaccade trials, but individuals with schizophrenia showed significantly lower pupil dilation compared to healthy subjects in antisaccade trials. Importantly, reduced preparatory pupil dilation for antisaccade trials was associated with worse general symptomatology in individuals with schizophrenia.

Discussion

Our findings suggest that changes in LC-NA activity - measured by task-evoked pupil dilation - when task demand increases is associated with schizophrenia symptoms. Interventions targeting the modulation of noradrenergic responses may be suitable candidates to reduce schizophrenia symptomatology.

The Gut-Brain Axis in Schizophrenia: The Implications of the Gut Microbiome and SCFA Production

Schizophrenia, a severe mental illness affecting about 1% of the population, manifests during young adulthood, leading to abnormal mental function and behavior. Its multifactorial etiology involves genetic factors, experiences of adversity, infection, and gene-environment interactions. Emerging research indicates that maternal infection or stress during pregnancy may also increase schizophrenia risk in offspring. Recent research on the gut-brain axis highlights the gut microbiome's potential influence on central nervous system (CNS) function and mental health, including schizophrenia. The gut microbiota, located in the digestive system, has a significant role to play in human physiology, affecting immune system development, vitamin synthesis, and protection against pathogenic bacteria. Disruptions to the gut microbiota, caused by diet, medication use, environmental pollutants, and stress, may lead to imbalances with far-reaching effects on CNS function and mental health. Of interest are short-chain fatty acids (SCFAs), metabolic byproducts produced by gut microbes during fermentation. SCFAs can cross the blood-brain barrier, influencing CNS activity, including microglia and cytokine modulation. The dysregulation of neurotransmitters produced by gut microbes may contribute to CNS disorders, including schizophrenia. This review explores the potential relationship between SCFAs, the gut microbiome, and schizophrenia. Our aim is to deepen the understanding of the gut-brain axis in schizophrenia and to elucidate its implications for future research and therapeutic approaches.

Maternal diabetes decreases the expression of α2-adrenergic and M2 muscarinic receptors in the visual cortex of male rat neonates

AIMS

This study investigates the impact of maternal diabetes on the expression of α2-adrenergic and M2 muscarinic receptors in the primary visual cortex of male offspring born to diabetic rats.

MAIN METHODS

In adult female rats, a single dose of intraperitoneal streptozotocin (STZ) was used to induce diabetes (Diabetic group). Diabetes was controlled with insulin in the Insulin-treated group. Female rats in the control group received normal saline instead of STZ. Male newborns were euthanized at P0, P7, and P14, and the expression of α2-adrenergic and M2 muscarinic receptors in the primary visual cortex was determined using immunohistochemistry (IHC).

KEY FINDINGS

The study showed that α2-adrenergic and M2 muscarinic receptors were significantly suppressed in all layers of the primary visual cortex of male neonates born to diabetic rats at P0, P7, and P14 compared to the control group. The highest expression was for the Con group at P14 and the lowest one was in the Dia group at P0 for both receptors. The insulin treatment in diabetic mothers modulated the expression of these receptors to normal levels in their newborns.

SIGNIFICANCE

The results demonstrate maternal diabetes decreases the expression of α2-adrenergic and M2 muscarinic receptors in the primary visual cortex of male offspring born to diabetic rats. Insulin treatment can offset these effects of diabetes.

The Neurobiological Underpinnings of Obsessive-Compulsive Symptoms in Psychosis, Translational Issues for Treatment-Resistant Schizophrenia

Almost 25% of schizophrenia patients suffer from obsessive-compulsive symptoms (OCS) considered a transdiagnostic clinical continuum. The presence of symptoms pertaining to both schizophrenia and obsessive-compulsive disorder (OCD) may complicate pharmacological treatment and could contribute to lack or poor response to the therapy. Despite the clinical relevance, no reviews have been recently published on the possible neurobiological underpinnings of this comorbidity, which is still unclear. An integrative view exploring this topic should take into account the following aspects: (i) the implication for glutamate, dopamine, and serotonin neurotransmission as demonstrated by genetic findings; (ii) the growing neuroimaging evidence of the common brain regions and dysfunctional circuits involved in both diseases; (iii) the pharmacological modulation of dopaminergic, serotoninergic, and glutamatergic systems as current therapeutic strategies in schizophrenia OCS; (iv) the recent discovery of midbrain dopamine neurons and dopamine D1- and D2-like receptors as orchestrating hubs in repetitive and psychotic behaviors; (v) the contribution of N-methyl-D-aspartate receptor subunits to both psychosis and OCD neurobiology. Finally, we discuss the potential role of the postsynaptic density as a structural and functional hub for multiple molecular signaling both in schizophrenia and OCD pathophysiology.

Dual orexin/hypocretin receptor antagonism attenuates NMDA receptor hypofunction-induced attentional impairments in a rat model of schizophrenia

Schizophrenia is a neuropsychiatric condition that is associated with impaired attentional processing and performance. Failure to support increasing attentional load may result, in part, from inhibitory failure in attention-relevant cortical regions, and available antipsychotics often fail to address this issue. Orexin/hypocretin receptors are found throughout the brain and are expressed on neurons relevant to both attention and schizophrenia, highlighting them as a potential target to treat schizophrenia-associated attentional dysfunction. In the present experiment, rats (N = 14) trained in a visual sustained attention task that required discrimination of trials which presented a visual signal from trials during which no signal was presented. Once trained, rats were then co-administered the psychotomimetic N-methyl-D-aspartate (NMDA) receptor antagonist dizocilpine (MK-801: 0 or 0.1 mg/kg, intraperitoneal injections) and the dual orexin receptor antagonist filorexant (MK-6096: 0, 0.1, or 1 mM, intracerebroventricular infusions) prior to task performance across six sessions. Dizocilpine impaired overall accuracy during signal trials, slowed reaction times for correctly-responded trials, and increased the number of omitted trials throughout the task. Dizocilpine-induced increases in signal trial deficits, correct response latencies, and errors of omission were reduced following infusions of the 0.1 mM, but not 1 mM, dose of filorexant. As such, orexin receptor blockade may improve attentional deficits in a state of NMDA receptor hypofunction.

Dopamine and norepinephrine differentially mediate the exploration-exploitation tradeoff

The catecholamines dopamine (DA) and norepinephrine (NE) have been repeatedly implicated in neuropsychiatric vulnerability, in part via their roles in mediating the decision making processes. Although the two neuromodulators share a synthesis pathway and are co-activated under states of arousal, they engage in distinct circuits and roles in modulating neural activity across the brain. However, in the computational neuroscience literature, they have been assigned similar roles in modulating the latent cognitive processes of decision making, in particular the exploration-exploitation tradeoff. Revealing how each neuromodulator contributes to this explore-exploit process will be important in guiding mechanistic hypotheses emerging from computational psychiatric approaches. To understand the differences and overlaps of the roles of these two catecholamine systems in regulating exploration and exploitation, a direct comparison using the same dynamic decision making task is needed. Here, we ran mice in a restless two-armed bandit task, which encourages both exploration and exploitation. We systemically administered a nonselective DA receptor antagonist (flupenthixol), a nonselective DA receptor agonist (apomorphine), a NE beta-receptor antagonist (propranolol), and a NE beta-receptor agonist (isoproterenol), and examined changes in exploration within subjects across sessions. We found a bidirectional modulatory effect of dopamine receptor activity on the level of exploration. Increasing dopamine activity decreased exploration and decreasing dopamine activity increased exploration. Beta-noradrenergic receptor activity also modulated exploration, but the modulatory effect was mediated by sex. Reinforcement learning model parameters suggested that dopamine modulation affected exploration via decision noise and norepinephrine modulation affected exploration via outcome sensitivity. Together, these findings suggested that the mechanisms that govern the transition between exploration and exploitation are sensitive to changes in both catecholamine functions and revealed differential roles for NE and DA in mediating exploration.

Structural and functional characterization of the locus coeruleus in young and late middle-aged individuals

INTRODUCTION

The brainstem locus coeruleus (LC) influences a broad range of brain processes, including cognition. The so-called LC contrast is an accepted marker of the integrity of the LC that consists of a local hyperintensity on specific Magnetic Resonance Imaging (MRI) structural images. The small size of the LC has, however, rendered its functional characterization difficult in humans, including in aging. A full characterization of the structural and functional characteristics of the LC in healthy young and late middle-aged individuals is needed to determine the potential roles of the LC in different medical conditions. Here, we wanted to determine whether the activation of the LC in a mismatch negativity task changes in aging and whether the LC functional response was associated to the LC contrast.

METHODS

We used Ultra-High Field (UHF) 7-Tesla functional MRI (fMRI) to record brain response during an auditory oddball task in 53 healthy volunteers, including 34 younger (age: 22.15y ± 3.27; 29 women) and 19 late middle-aged (age: 61.05y ± 5.3; 14 women) individuals.

RESULTS

Whole-brain analyses confirmed brain responses in the typical cortical and subcortical regions previously associated with mismatch negativity. When focusing on the brainstem, we found a significant response in the rostral part of the LC probability mask generated based on individual LC images. Although bilateral, the activation was more extensive in the left LC. Individual LC activity was not significantly different between young and late middle-aged individuals. Importantly, while the LC contrast was higher in older individuals, the functional response of the LC was not significantly associated with its contrast.

DISCUSSION

These findings may suggest that the age-related alterations of the LC structural integrity may not be related to changes in its functional response. The results further suggest that LC responses may remain stable in healthy individuals aged 20 to 70.

Biomarkers in the cerebrospinal fluid of patients with psychotic disorders compared to healthy controls: a systematic review and meta-analysis

Psychotic disorders are severe mental disorders with poorly understood etiology. Biomarkers in the cerebrospinal fluid (CSF) could provide etiological clues and diagnostic tools for psychosis; however, an unbiased overview of CSF alterations in individuals with psychotic disorders is lacking. The objective of this study was to summarize all quantifiable findings in CSF from individuals with psychotic disorders compared to healthy controls (HC). Studies published before January 25th, 2023 were identified searching PubMed, EMBASE, Cochrane Library, Web of Science, ClinicalTrials.gov, and PsycINFO. Screening, full-text review, data extraction, and risk of bias assessments were performed by two independent reviewers following PRISMA guidelines. Findings in patients and healthy controls were compared and summarized using random-effects analyses and assessment of publication bias, subgroup and sensitivity analyses were performed. 145 studies, covering 197 biomarkers, were included, of which 163 biomarkers have not previously been investigated in meta-analyses. All studies showed some degree of bias. 55 biomarkers measured in CSF were associated with psychosis and of these were 15 biomarkers measured in ≥2 studies. Patients showed increased levels of noradrenaline (standardized mean difference/SMD, 0.53; 95% confidence interval/CI, 0.16 to 0.90) and its metabolite 3-methoxy-4-hydroxyphenylglycol (SMD, 0.30; 95% CI: 0.05 to 0.55), the serotonin metabolite 5-hydroxyindoleacetic acid (SMD, 0.11; 95% CI: 0.01 to 0.21), the pro-inflammatory neurotransmitter kynurenic acid (SMD, 1.58; 95% CI: 0.34 to 2.81), its precursor kynurenine (SMD,0.99; 95% CI: 0.60 to 1.38), the cytokines interleukin-6 (SMD, 0.58; 95% CI: 0.39 to 0.77) and interleukin-8 (SMD, 0.43; 95% CI: 0.24 to 0.62), the endocannabinoid anandamide (SMD, 0.78; 95% CI: 0.53 to 1.02), albumin ratio (SMD, 0.40; 95% CI: 0.08 to 0.72), total protein (SMD, 0.29; 95% CI: 0.16 to 0.43), immunoglobulin ratio (SMD, 0.45; 95% CI: 0.06 to 0.85) and glucose (SMD, 0.48; 95% CI: 0.01 to 0.94). Neurotensin (SMD, -0.67; 95% CI: -0.89 to -0.46) and γ-aminobutyric acid (SMD, -0.29; 95% CI: -0.50 to -0.09) were decreased. Most biomarkers showed no significant differences, including the dopamine metabolites homovanillic acid and 3,4-dihydroxyphenylacetic acid. These findings suggest that dysregulation of the immune and adrenergic system as well as blood-brain barrier dysfunction are implicated in the pathophysiology of psychotic disorders.

Functional and phosphoproteomic analysis of β-adrenergic receptor signaling at excitatory synapses in the CA1 region of the ventral hippocampus

Activation of β-adrenergic receptors (β-ARs) not only enhances learning and memory but also facilitates the induction of long-term potentiation (LTP), a form of synaptic plasticity involved in memory formation. To identify the mechanisms underlying β-AR-dependent forms of LTP we examined the effects of the β-AR agonist isoproterenol on LTP induction at excitatory synapses onto CA1 pyramidal cells in the ventral hippocampus. LTP induction at these synapses is inhibited by activation of SK-type K⁺ channels, suggesting that β-AR activation might facilitate LTP induction by inhibiting SK channels. However, although the SK channel blocker apamin enhanced LTP induction, it did not fully mimic the effects of isoproterenol. We therefore searched for potential alternative mechanisms using liquid chromatography-tandem mass spectrometry to determine how β-AR activation regulates phosphorylation of postsynaptic density (PSD) proteins. Strikingly, β-AR activation regulated hundreds of phosphorylation sites in PSD proteins that have diverse roles in dendritic spine structure and function. Moreover, within the core scaffold machinery of the PSD, β-AR activation increased phosphorylation at several sites previously shown to be phosphorylated after LTP induction. Together, our results suggest that β-AR activation recruits a diverse set of signaling pathways that likely act in a concerted fashion to regulate LTP induction.

Influence of vigilance-related arousal on brain dynamics: Potentials of new approaches

Growing research has focused on how mesoscopic activity in the brain develops over time and space. Recent influential studies using functional imaging have characterized brain dynamics in terms of the spread of activation across the brain following a unimodal to transmodal axis. In parallel, a number of studies have assessed changes of brain connectivity in terms of vigilance-linked arousal. Here I offer a view on how these two lines of research can lead to a deeper understanding of how arousal shapes the brain's dynamic behavior. This knowledge could have great impact on the investigation of mental disease.

The interaction between first-episode drug-naïve schizophrenia and age based on gray matter volume and its molecular analysis: a multimodal magnetic resonance imaging study

OBJECTIVES

Schizophrenia is a neurodevelopmental disorder characterized by progressive and widespread gray matter (GM) atrophy. Studies have shown that normal brain development has an impact on schizophrenia-induced GM alterations. However, the neuropathology and underlying molecular mechanisms of interaction between age and schizophrenia are unclear.

METHODS

This study enrolled 66/84 first-episode drug-naïve patients with early-onset/adult-onset schizophrenia ((EOS)/(AOS)) and matched normal controls (NC) (46 adolescents/73 adults), undergoing T1-weighted high-resolution magnetic resonance imaging. Gray matter volume (GMV) in four groups was detected using 2-way analyses of variance with diagnosis and age as factors. Then, factors-related volume maps and neurotransmitter maps were spatially correlated using JuSpace to determine the relationship to molecular structure.

RESULTS

Compared to AOS, EOS and adult NC had larger GMV in right middle frontal gyrus. Compared to adolescent NC, EOS and adult NC had smaller GMV in right lingual gyrus, right fusiform gyrus, and right cerebellum_6. Disease-induced GMV reductions were mainly distributed in frontal, parietal, thalamus, visual, motor cortex, and medial temporal lobe structures. Age-induced GMV alterations were mainly distributed in visual and motor cortex. The changed GMV induced by schizophrenia, age, and their interaction was related to dopaminergic and serotonergic receptors. Age is also related to glutamate receptors, and schizophrenia is also associated with GABAaergic and noradrenergic receptors.

CONCLUSIONS

Our results revealed the multimodal neural mechanism of interaction between disease and age. We emphasized age-related GM abnormalities of ventral stream of visual perceptual pathways and high-level cognitive brain in EOS, which may be affected by imbalance of excitatory and inhibitory neurotransmitters.

Apathy in Alzheimer's disease: A neurocircuitry based perspective

In addition to memory deficits and other cognitive disturbances, patients with Alzheimer's disease (AD) experience neuropsychiatric symptoms, notably apathy, which is a state of impaired motivation observed by deficits in goal directed behavior. Apathy is a multifaceted neuropsychiatric condition and appears to be a prognostic indicator, correlating with the progression of AD. Strikingly, recent studies point out that the neurodegenerative pathology of AD may drive apathy independent of cognitive decline. These studies also highlight that neuropsychiatric symptoms, in particular apathy, might manifest early in AD. Here, we review the current understanding of the neurobiological underpinnings of apathy as a neuropsychiatric symptom of AD. Specifically, we highlight the neural circuits and brain regions recognized to be correlated with the apathetic symptomatology. We also discuss the current evidence that supports the notion that apathy and cognitive deficits may develop as independent but concurrent phenomena driven by AD pathology, suggesting its efficacy as an additional outcome measure in Alzheimer's disease clinical trials. The current and prospective therapeutic interventions for apathy in AD from a neurocircuitry based perspective are also reviewed.

Common mechanisms underlying axonal transport deficits in neurodegenerative diseases: a mini review

Many neurodegenerative diseases including Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis are characterized by the accumulation of pathogenic proteins and abnormal localization of organelles. These pathological features may be related to axonal transport deficits in neurons, which lead to failures in pathological protein targeting to specific sites for degradation and organelle transportation to designated areas needed for normal physiological functioning. Axonal transport deficits are most likely early pathological events in such diseases and gradually lead to the loss of axonal integrity and other degenerative changes. In this review, we investigated reports of mechanisms underlying the development of axonal transport deficits in a variety of common neurodegenerative diseases, such as Alzheimer's disease, amyotrophic lateral sclerosis, Parkinson's disease and Huntington's disease to provide new ideas for therapeutic targets that may be used early in the disease process. The mechanisms can be summarized as follows: (1) motor protein changes including expression levels and post-translational modification alteration; (2) changes in microtubules including reducing stability and disrupting tracks; (3) changes in cargoes including diminished binding to motor proteins. Future studies should determine which axonal transport defects are disease-specific and whether they are suitable therapeutic targets in neurodegenerative diseases.

Locus Coeruleus Neurons' Firing Pattern Is Regulated by ERG Voltage-Gated K+ Channels

Locus coeruleus (LC) neurons, with their extensive innervations throughout the brain, control a broad range of physiological processes. Several ion channels have been characterized in LC neurons that control intrinsic membrane properties and excitability. However, ERG (ether-à-go-go-related gene) K⁺ channels that are particularly important in setting neuronal firing rhythms and automaticity have not as yet been discovered in the LC. Moreover, the neurophysiological and pathophysiological roles of ERG channels in the brain remain unclear despite their expression in several structures. By performing immunohistochemical investigations, we found that ERG-1A, ERG-1B, ERG-2 and ERG-3 are highly expressed in the LC neurons of mice. To examine the functional role of ERG channels, current-clamp recordings were performed on mouse LC neurons in brain slices under visual control. ERG channel blockade by WAY-123,398, a class III anti-arrhythmic agent, increased the spontaneous firing activity and discharge irregularity of LC neurons. Here, we have shown the presence of distinct ERG channel subunits in the LC which play an imperative role in modulating neuronal discharge patterns. Thus, we propose that ERG channels are important players behind the changes in, and/or maintenance of, LC firing patterns that are implicated in the generation of different behaviors and in several disorders.

Plasma Amino Acids and Acylcarnitines Are Associated with the Female but Not Male Adolescent Swimmer's Performance: An Integration between Mass Spectrometry and Complex Network Approaches

The main aim of this study was to compare the performance over different distances, the critical velocity (CV), and plasma acylcarnitines/amino acids of male and female adolescent swimmers. Moreover, we applied the complex network approach to identify which molecules are associated with athletes' performances. On the first day under a controlled environment, blood samples were collected after 12 h of overnight fasting. Performance trials (100, 200, 400, and 800-m) were randomly performed in the subsequent four days in a swimming pool, and CV was determined by linear distance versus time mathematical function. Metabolomic analyses were carried out on a triple quadrupole mass spectrometer performing electrospray ionization in the positive ionization mode. No difference was observed between the performance of male and female swimmers. Except for 200-m distance (p = 0.08), plasma tyrosine was positively and significantly associated with the female times during the trials (100-m, p = 0.04; 400-m, p = 0.04; 800-m, p = 0.02), and inversely associated with the CV (p = 0.02). The complex network approach showed that glycine (0.406), glutamine (0.400), arginine (0.335), free carnitine (0.355), tryptophan (0.289), and histidine (0.271) were the most influential nodes to reach tyrosine. These results revealed a thread that must be explored in further randomized/controlled designs, improving the knowledge surrounding nutrition and the performance of adolescent swimmers.

Catecholaminergic cell type-specific expression of Cre recombinase in knock-in transgenic rats generated by the Combi-CRISPR technology

BACKGROUND

Cell groups containing catecholamines provide a useful model to study the molecular and cellular mechanisms underlying the morphogenesis, physiology, and pathology of the central nervous system. For this purpose, it is necessary to establish a system to induce catecholaminergic group-specific expression of Cre recombinase. Recently, we introduced a gene cassette encoding 2A peptide fused to Cre recombinase into the site between the C-terminus and translational termination codons of the rat tyrosine hydroxylase (TH) open reading frame by the Combi-CRISPR technology, which is a genomic editing method to enable an efficient knock-in (KI) of long DNA sequence into a target site. However, the expression patterns of the transgene and its function as well as the effect of the mutation on the biochemical and behavioral phenotypes in the KI strains have not been characterized yet.

NEW METHOD

We aimed to evaluate the usefulness of TH-Cre KI rats as an experimental model for investigating the structure and function of catecholaminergic neurons in the brain.

RESULTS

We detected cell type-specific expression of Cre recombinase and site-specific recombination activity in the representative catecholaminergic groups in the TH-Cre KI rat strains. In addition, we measured TH protein levels and catecholamine accumulation in the brain regions, as well as motor, reward-related, and anxiety-like behaviors, indicating that catecholamine metabolism and general behavior are apparently normal in these KI rats.

CONCLUSIONS

TH-Cre KI rat strains produced by the Combi-CRISPR system offer a beneficial model to study the molecular and cellular mechanics for the morphogenesis, physiology, and pathology of catecholamine-containing neurons in the brain.

Excitatory and inhibitory effects of HCN channel modulation on excitability of layer V pyramidal cells

Dendrites of cortical pyramidal cells are densely populated by hyperpolarization-activated cyclic nucleotide-gated (HCN) channels, a.k.a. Ih channels. Ih channels are targeted by multiple neuromodulatory pathways, and thus are one of the key ion-channel populations regulating the pyramidal cell activity. Previous observations and theories attribute opposing effects of the Ih channels on neuronal excitability due to their mildly hyperpolarized reversal potential. These effects are difficult to measure experimentally due to the fine spatiotemporal landscape of the Ih activity in the dendrites, but computational models provide an efficient tool for studying this question in a reduced but generalizable setting. In this work, we build upon existing biophysically detailed models of thick-tufted layer V pyramidal cells and model the effects of over- and under-expression of Ih channels as well as their neuromodulation. We show that Ih channels facilitate the action potentials of layer V pyramidal cells in response to proximal dendritic stimulus while they hinder the action potentials in response to distal dendritic stimulus at the apical dendrite. We also show that the inhibitory action of the Ih channels in layer V pyramidal cells is due to the interactions between Ih channels and a hot zone of low voltage-activated Ca2+ channels at the apical dendrite. Our simulations suggest that a combination of Ih-enhancing neuromodulation at the proximal part of the apical dendrite and Ih-inhibiting modulation at the distal part of the apical dendrite can increase the layer V pyramidal excitability more than either of the two alone. Our analyses uncover the effects of Ih-channel neuromodulation of layer V pyramidal cells at a single-cell level and shed light on how these neurons integrate information and enable higher-order functions of the brain.

Pupil size and pupillary light reflex in early infancy: heritability and link to genetic liability to schizophrenia

BACKGROUND

Measures based on pupillometry, such as the pupillary light reflex (PLR) and baseline pupil size, reflect physiological responses linked to specific neural circuits that have been implicated as atypical in some psychiatric and neurodevelopmental conditions.

METHODS

We investigated the contribution of genetic and environmental factors to the baseline pupil size and the PLR in 510 infant twins assessed at 5 months of age (281 monozygotic and 229 dizygotic pairs), and its associations with common genetic variants associated with neurodevelopmental (autism spectrum disorder and attention deficit hyperactivity disorder) and mental health (bipolar disorder, major depressive disorder and schizophrenia) conditions using genome-wide polygenic scores (GPSs).

RESULTS

Univariate twin modelling showed high heritability at 5 months for both pupil size (h²  = .64) and constriction in response to light (h²  = .62), and bivariate twin modeling indicated substantial independence between the genetic factors influencing each (r_G  = .38). A statistically significant positive association between infant tonic pupil size and the GPS for schizophrenia was found (β = .15, p = .024), while there was no significant association with the GPS for autism or any other GPSs.

CONCLUSIONS

This study shows that some pupil measures are highly heritable in early infancy, although substantially independent in their genetic etiologies, and associated with common genetic variants linked to schizophrenia. It illustrates how genetically informed studies of infants may help us understand early physiological responses associated with psychiatric disorders which emerge much later in life.

Brain anomalies in early psychosis: From secondary to primary psychosis

Brain anomalies are frequently found in early psychoses. Although they may remain undetected for many years, their interpretation is critical for differential diagnosis. In secondary psychoses, their identification may allow specific management. They may also shed light on various pathophysiological aspects of primary psychoses. Here we reviewed cases of secondary psychoses associated with brain anomalies, reported over a 20-year period in adolescents and young adults aged 13-30 years old. We considered age at first psychotic symptoms, relevant medical history, the nature of psychiatric symptoms, clinical red flags, the nature of the brain anomaly reported, and the underlying disease. We discuss the relevance of each brain area in light of normal brain function, recent case-control studies, and postulated pathophysiology. We show that anomalies in all regions, whether diffuse, multifocal, or highly localized, may lead to psychosis, without necessarily being associated with non-psychiatric symptoms. This underlines the interest of neuroimaging in the initial workup, and supports the hypothesis of psychosis as a global network dysfunction that involves many different regions.

Spared performance but increased uncertainty in schizophrenia: Evidence from a probabilistic decision-making task

Aberrant attribution of salience to in fact little informative events might explain the emergence of positive symptoms in schizophrenia and has been linked to belief uncertainty. Uncertainty is thought to be encoded by neuromodulators, including norepinephrine. However, norepinephrinergic encoding of uncertainty, measured as task-related pupil dilation, has rarely been explored in schizophrenia. Here, we addressed this question by comparing individuals with a disorder from the schizophrenia spectrum to a non-psychiatric control group on behavioral and pupillometric measures in a probabilistic prediction task, where different levels of uncertainty were introduced. Behaviorally, patients performed similar to controls, but their belief uncertainty was higher, particularly when instability of the task environment was high, suggesting an increased sensitivity to this instability. Furthermore, while pupil dilation scaled positively with uncertainty, this was less the case for patients, suggesting aberrant neuromodulatory regulation of neural gain, which may hinder the reduction of uncertainty in the long run. Together, the findings point to abnormal uncertainty processing and norepinephrinergic signaling in schizophrenia, potentially informing future development of both psychopharmacological therapies and psychotherapeutic approaches that deal with the processing of uncertain information.

Abnormal synaptic plasticity and impaired cognition in schizophrenia

Schizophrenia (SCZ) is a severe mental illness that affects several brain domains with relation to cognition and behaviour. SCZ symptoms are typically classified into three categories, namely, positive, negative, and cognitive. The etiology of SCZ is thought to be multifactorial and poorly understood. Accumulating evidence has indicated abnormal synaptic plasticity and cognitive impairments in SCZ. Synaptic plasticity is thought to be induced at appropriate synapses during memory formation and has a critical role in the cognitive symptoms of SCZ. Many factors, including synaptic structure changes, aberrant expression of plasticity-related genes, and abnormal synaptic transmission, may influence synaptic plasticity and play vital roles in SCZ. In this article, we briefly summarize the morphology of the synapse, the neurobiology of synaptic plasticity, and the role of synaptic plasticity, and review potential mechanisms underlying abnormal synaptic plasticity in SCZ. These abnormalities involve dendritic spines, postsynaptic density, and long-term potentiation-like plasticity. We also focus on cognitive dysfunction, which reflects impaired connectivity in SCZ. Additionally, the potential targets for the treatment of SCZ are discussed in this article. Therefore, understanding abnormal synaptic plasticity and impaired cognition in SCZ has an essential role in drug therapy.

The Effect of Glutathione Deficit During Early Postnatal Brain Development on the Prepulse Inhibition and Monoamine Levels in Brain Structures of Adult Sprague-Dawley Rats

Recent studies suggest that impaired glutathione synthesis and distorted dopaminergic transmission are important factors in the pathophysiology of schizophrenia. In the present study, on the postnatal days p5-p16, male pups were treated with the inhibitor of glutathione synthesis, L-buthionine-(S,R)- sulfoximine (BSO, 3.8 or 7.6 mmol/kg), and the dopamine uptake inhibitor, GBR 12,909 (5 mg/kg) alone or in combination, and prepulse inhibition of the acoustic startle response (PPI) was evaluated in adult 90-day-old rats. Moreover, the monoamine levels in the cortex and hippocampus of 16-day-old rats or 91-day-old rats were measured. The present results showed that administration of BSO at 3.8 mmol/kg led to a decreasing tendency in PPI for all tested prepulse intensities. In contrast, a combined treatment with BSO in both studied doses and GBR 12,909 did not induce significant deficits in PPI. Moreover, the results of biochemical studies indicated that treatment with BSO or GBR 12,909 alone induced a weak increase in the activity of dopaminergic, serotonergic, and noradrenergic systems in the frontal cortex and hippocampus of 16-day-old rats and 91-day-old rats. However, the combined administration of both substances allowed for maintaining the normal activity of monoaminergic systems in the rat brain. The most significant changes in the functioning of monoaminergic systems were observed in the frontal cortex of 16-day-old rats. Therefore, it seems that the frontal cortex of rat puppies is most sensitive to glutathione deficiencies resulting in increased oxidative stress in neurons. As a result, it can lead to cognitive and memory impairment.

Do propranolol and amisulpride modulate confidence in risk-taking?

Background: Making rational choices and being able to consciously reflect on the goodness of these choices is important for successfully navigating the world. Value-based decisions have been extensively studied, but we know little about the factors that influence our confidence in value-based choice. Particularly, we know very little about the neurotransmitters that may mediate these processes.  Methods: In this double-blind, placebo-controlled study design involving 61 healthy human subjects (30 female), we assessed the contributions of dopamine (400 mg amisulpride) and noradrenaline (40 mg propranolol) to value-based decision making and the subjective confidence therein in a monetary risky gambling task.  Results: We did not find any significant effect of either of the two pharmacological manipulations, neither on value-based decision making, nor on subjective confidence.   Conclusion: We discuss these (null) findings, and release all relevant data and code. This will allow researchers to further interrogate the data, to counteract publication biases in favour of significant findings, and to use our study as a source for balanced meta-analyses.

Ketamine for psychotic depression: An overview of the glutamatergic system and ketamine's mechanisms associated with antidepressant and psychotomimetic effects

Approximately 0.35-1% of the general population is afflicted with psychotic depression at some time in their life. Psychotic depression is a subtype of major depressive disorder characterized by mood congruent hallucinations and/or delusions. Patients with psychotic depression often represent the most severe cases, with high relapse and mortality rate. Although treatment guidelines recommend a combination of antidepressants and antipsychotics or electroconvulsive therapy, most patients subsequently relapse due to treatment resistance. Furthermore, with the concern of antipsychotic drug's side effects (e.g., tardive dyskinesia), there is a need for an alternative pharmacotherapy for psychotic depression. Recently, several case studies demonstrated that treatment with ketamine not only ameliorated mood, but also improved psychotic symptoms in patients with treatment-resistant depression and psychotic features. However, the safety of ketamine in these patients is controversial since ketamine is known to induce psychotomimetic and dissociative effects. Additionally, the efficacy and safety of ketamine in patients with psychotic depression has not been established as most clinical trials have excluded these persons due to the theorized risk of aggravating psychotic symptoms. Notwithstanding, it is not established empirically that ketamine treatment in psychotic depression would predictably amplify psychotic symptoms and/or overall illness presentation. Future trials evaluating ketamine in depression should include patients with psychotic features to inform whether ketamine is safe and effective in this subpopulation.

A Potential Interface between the Kynurenine Pathway and Autonomic Imbalance in Schizophrenia

Schizophrenia is a neuropsychiatric disorder characterized by various symptoms including autonomic imbalance. These disturbances involve almost all autonomic functions and might contribute to poor medication compliance, worsened quality of life and increased mortality. Therefore, it has a great importance to find a potential therapeutic solution to improve the autonomic disturbances. The altered level of kynurenines (e.g., kynurenic acid), as tryptophan metabolites, is almost the most consistently found biochemical abnormality in schizophrenia. Kynurenic acid influences different types of receptors, most of them involved in the pathophysiology of schizophrenia. Only few data suggest that kynurenines might have effects on multiple autonomic functions. Publications so far have discussed the implication of kynurenines and the alteration of the autonomic nervous system in schizophrenia independently from each other. Thus, the coupling between them has not yet been addressed in schizophrenia, although their direct common points, potential interfaces indicate the consideration of their interaction. The present review gathers autonomic disturbances, the impaired kynurenine pathway in schizophrenia, and the effects of kynurenine pathway on autonomic functions. In the last part of the review, the potential interaction between the two systems in schizophrenia, and the possible therapeutic options are discussed.

DNA methylome perturbations: an epigenetic basis for the emergingly heritable neurodevelopmental abnormalities associated with maternal smoking and maternal nicotine exposure†

Maternal smoking during pregnancy is associated with an ensemble of neurodevelopmental consequences in children and therefore constitutes a pressing public health concern. Adding to this burden, contemporary epidemiological and especially animal model research suggests that grandmaternal smoking is similarly associated with neurodevelopmental abnormalities in grandchildren, indicative of intergenerational transmission of the neurodevelopmental impacts of maternal smoking. Probing the mechanistic bases of neurodevelopmental anomalies in the children of maternal smokers and the intergenerational transmission thereof, emerging research intimates that epigenetic changes, namely DNA methylome perturbations, are key factors. Altogether, these findings warrant future research to fully elucidate the etiology of neurodevelopmental impairments in the children and grandchildren of maternal smokers and underscore the clear potential thereof to benefit public health by informing the development and implementation of preventative measures, prophylactics, and treatments. To this end, the present review aims to encapsulate the burgeoning evidence linking maternal smoking to intergenerational epigenetic inheritance of neurodevelopmental abnormalities, to identify the strengths and weaknesses thereof, and to highlight areas of emphasis for future human and animal model research therein.

The Role of the Second Extracellular Loop of Norepinephrine Transporter, Neurotrophin-3 and Tropomyosin Receptor Kinase C in T Cells: A Peripheral Biomarker in the Etiology of Schizophrenia

The neurobiology of schizophrenia is multifactorial, comprising the dysregulation of several biochemical pathways and molecules. This research proposes a peripheral biomarker for schizophrenia that involves the second extracellular loop of norepinephrine transporter (NEText), the tropomyosin receptor kinase C (TrkC), and the neurotrophin-3 (NT-3) in T cells. The study of NEText, NT-3, and TrkC was performed in T cells and plasma extracted from peripheral blood of 54 patients with schizophrenia and 54 healthy controls. Levels of NT-3, TrkC, and NET were significantly lower in plasma and T cells of patients compared to healthy controls. Co-immunoprecipitation (co-IPs) showed protein interactions with Co-IP NEText–NT-3 and Co-IP NEText–TrkC. Computational modelling of protein–peptide docking by CABS-dock provided a medium–high accuracy model for NT-3–NEText (4.6935 Å) and TrkC–NEText (2.1365 Å). In summary, immunocomplexes reached statistical relevance in the T cells of the control group contrary to the results obtained with schizophrenia. The reduced expression of NT-3, TrkC, and NET, and the lack of molecular complexes in T cells of patients with schizophrenia may lead to a peripheral dysregulation of intracellular signaling pathways and an abnormal reuptake of norepinephrine (NE) by NET. This peripheral molecular biomarker underlying schizophrenia reinforces the role of neurotrophins, and noradrenergic and immune systems in the pathophysiology of schizophrenia.

Pupil-based States of Brain Integration across Cognitive States

Arousal is a potent mechanism that provides the brain with functional flexibility and adaptability to external conditions. Within the wake state, arousal levels driven by activity in the neuromodulatory systems are related to specific signatures of neural activation and brain synchrony. However, direct evidence is still lacking on the varying effects of arousal on macroscopic brain characteristics and across a variety of cognitive states in humans. Using a concurrent fMRI-pupillometry approach, we used pupil size as a proxy for arousal and obtained patterns of brain integration associated with increasing arousal levels. We carried out this analysis on resting-state data and data from two attentional tasks implicating different cognitive processes. We found that an increasing level of arousal was related to a state of increased brain integration. This effect was prominent in the salience, visual and default-mode networks in all conditions, while other regions showed task-specificity. Increased integration in the salience network was also related to faster pupil dilation in the two attentional tasks. Furthermore, task performance was related to arousal level, with lower accuracy at higher level of arousal. Taken together, our study provides evidence in humans for pupil size as an index of brain network state, and supports the role of arousal as a switch that drives brain coordination in specific brain regions according to the cognitive state.

Minireview: Animal model of schizophrenia from the perspective of behavioral pharmacology: Effect of treatment on cognitive functions

Schizophrenia is a debilitating mental disorder characterized by positive, negative and cognitive symptoms. Whereas positive symptoms are satisfactorily addressed by current antipsychotic treatment, negative and cognitive symptomatic treatment remains largely ineffective. This review investigates the treatment efficacy regarding cognitive symptoms and evaluates the contribution of different monoamine receptor systems involved in schizophrenia pathophysiology to cognition. In the review, we included preclinical studies assessing the effect of different treatments on cognition in pre-pulse inhibition and two spatial cognitive tests. While pre-pulse inhibition investigates pre-attentive processes operating outside of conscious awareness, the spatial tasks require continuous attention and active engagement in task solving for a successful outcome. The schizophrenia-like phenotype was attained by acute or subchronic administration of non-competitive NMDA receptor antagonist MK-801.

Othello syndrome in Parkinson's disease: a systematic review and report of a case series

INTRODUCTION

Psychosis in Parkinson's disease (PD) is common and consists of hallucinations, illusions, and delusions. Among the latter, delusional jealousy, also named Othello syndrome (OS), might impair the quality of life of both patients and their partners. We aimed to perform a systematic review and report a series of PD patients presenting with OS.

METHODS

A systematic review research was performed in PubMed database, excluding non-English articles, single case reports, reviews and neuropathology articles, comments, and articles concerning OS associated with deep brain stimulation (DBS) and levodopa-carbidopa intestinal gel infusion. We also described eleven PD patients (9 M and 2 F) with OS, identified in a cohort of consecutive 153 patients, comparing them with eleven matched no OS (nOS) PD subjects taken from the same cohort.

RESULTS

We included eight articles (four case series and four cross-sectional studies). OS resulted more common among males than females. We did not find higher levodopa dose and levodopa equivalent dose for dopamine agonists and for all anti-parkinsonian drugs in our OS group. In our case series, OS patients showed visual hallucinations (p=0.001) and a trend to have depression (p=0.080) more frequently than nOS ones.

CONCLUSIONS

OS is not a rare disorder in PD, probably due not only to abnormal dopaminergic stimulation but also to serotonergic dysfunction in biologically predisposed subjects. Visual hallucinations and other concomitant psychiatric diseases, in particular depression, might represent a risk factor for the OS development.

From Brain Organoids to Networking Assembloids: Implications for Neuroendocrinology and Stress Medicine

Brain organoids are three-dimensional cultures that contain multiple types of cells and cytoarchitectures, and resemble fetal human brain structurally and functionally. These organoids are being used increasingly to model brain development and disorders, however, they only partially recapitulate such processes, because of several limitations, including inability to mimic the distinct cortical layers, lack of functional neuronal circuitry as well as non-neural cells and gyrification, and increased cellular stress. Efforts to create improved brain organoid culture systems have led to region-specific organoids, vascularized organoids, glia-containing organoids, assembloids, sliced organoids and polarized organoids. Assembloids are fused region-specific organoids, which attempt to recapitulate inter-regional and inter-cellular interactions as well as neural circuitry development by combining multiple brain regions and/or cell lineages. As a result, assembloids can be used to model subtle functional aberrations that reflect complex neurodevelopmental, neuropsychiatric and neurodegenerative disorders. Mammalian organisms possess a highly complex neuroendocrine system, the stress system, whose main task is the preservation of systemic homeostasis, when the latter is threatened by adverse forces, the stressors. The main central parts of the stress system are the paraventricular nucleus of the hypothalamus and the locus caeruleus/norepinephrine-autonomic nervous system nuclei in the brainstem; these centers innervate each other and interact reciprocally as well as with various other CNS structures. Chronic dysregulation of the stress system has been implicated in major pathologies, the so-called chronic non-communicable diseases, including neuropsychiatric, neurodegenerative, cardiometabolic and autoimmune disorders, which lead to significant population morbidity and mortality. We speculate that brain organoids and/or assembloids could be used to model the development, regulation and dysregulation of the stress system and to better understand stress-related disorders. Novel brain organoid technologies, combined with high-throughput single-cell omics and gene editing, could, thus, have major implications for precision medicine.

Shedding light on the role of CX3CR1 in the pathogenesis of schizophrenia

Schizophrenia has a complex and heterogeneous molecular and clinical picture. Over the years of research on this disease, many factors have been suggested to contribute to its pathogenesis. Recently, the inflammatory processes have gained particular interest in the context of schizophrenia due to the increasing evidence from epidemiological, clinical and experimental studies. Within the immunological component, special attention has been brought to chemokines and their receptors. Among them, CX3C chemokine receptor 1 (CX3CR1), which belongs to the family of seven-transmembrane G protein-coupled receptors, and its cognate ligand (CX3CL1) constitute a unique system in the central nervous system. In the view of regulation of the brain homeostasis through immune response, as well as control of microglia reactivity, the CX3CL1–CX3CR1 system may represent an attractive target for further research and schizophrenia treatment. In the review, we described the general characteristics of the CX3CL1–CX3CR1 axis and the involvement of this signaling pathway in the physiological processes whose disruptions are reported to participate in mechanisms underlying schizophrenia. Furthermore, based on the available clinical and experimental data, we presented a guide to understanding the implication of the CX3CL1–CX3CR1 dysfunctions in the course of schizophrenia.

Locus Coeruleus Malfunction Is Linked to Psychopathology in Prodromal Dementia With Lewy Bodies

Background: The locus coeruleus (LC) is a nucleus in the human brainstem with a variety of noradrenaline-driven functions involved in cognition, emotions, and perception. Dementia with Lewy bodies (DLB) constitutes a neurodegenerative disease involving deposits of alpha-synuclein, first appearing in the brainstem. The goal of this narrative review is to delineate the relationship between the expression of psychiatric symptoms as an early-onset of DLB and the degeneration of the LC's noradrenaline system.

Methods: We searched in PubMed for relevant articles concerning LC degeneration and psychiatric symptoms in prodromal DLB in this narrative review. We rely on the McKeith criteria for prodromal psychiatric DLB.

Results: We found four studies that document neuronal loss, deposits of Lewy bodies and other hints for neurodegeneration in the LC in patients with DLB. Furthermore, we reviewed theories and studies on how the degenerated noradrenaline LC system contributes to psychiatric DLB's phenotype. We hypothesized how anxiety, hallucinations, delusions, and depressive symptoms might occur in DLB patients due to degenerated noradrenergic neurons entailing consecutive altered noradrenergic transmission in the LC's projection areas.

Conclusions: LC degeneration in prodromal DLB might cause psychiatric symptoms as the first and non-motor manifestation of DLB, as the LC is affected earlier by degeneration than are dopaminergic structures such as the substantia nigra, which are impaired later in the disease course.