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Suker S, Mihov Y, Wolf A, Mueller SV, Hasler G. Behavioral Response to Catecholamine Depletion in Individuals With Schizophrenia and Healthy Volunteers. SCHIZOPHRENIA BULLETIN OPEN 2023; 4:sgad023. [PMID: 39145346 PMCID: PMC11207692 DOI: 10.1093/schizbullopen/sgad023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 08/16/2024]
Abstract
Background and Hypothesis Dysfunction of the dopamine system is the leading neurobiological hypothesis of schizophrenia. In this study, we tested this hypothesis in the context of aberrance salience theory of delusions using catecholamine depletion. We hypothesized that acute dopamine depletion improves both positive symptoms and salience attribution in individuals with schizophrenia. Study Design Catecholamine depletion was achieved by oral administration of alpha-methyl-para-tyrosine (AMPT) in 15 individuals with schizophrenia and 15 healthy volunteers. The study design consisted of a randomized, double-blind, placebo-controlled crossover, single-site experimental trial. The main outcome measures were the Scale for the Assessment of Positive Symptoms and the Salience Attribution Test. Study Results Catecholamine depletion transiently reduced specific psychotic symptoms in symptomatic individuals with schizophrenia, namely delusions and positive formal thought disorder (interaction treatment-by-timepoint, P = .013 and P = .010, respectively). We also found trends for catecholamine depletion to increase relevant bias and adaptive salience in participants with schizophrenia while decreasing them in healthy controls (interaction group-by-treatment, P = .060 and P = .089, respectively). Exploratory analyses revealed that in participants with schizophrenia, higher relevant bias at 3 hours after the end of AMPT treatment corresponded to lower delusional symptoms (Spearman's rho = -0.761, P = .001). Conclusions This study suggests that the relationship between dopamine hyperactivity and delusional symptoms in schizophrenia is mediated by impaired attribution of salience to reward-predicting stimuli.
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Affiliation(s)
- Samir Suker
- Psychiatric University Hospital, University of Bern, Bern, Switzerland
| | - Yoan Mihov
- Unit of Psychiatry Research, University of Fribourg, Fribourg, Switzerland
| | - Andreas Wolf
- Psychiatric University Hospital, University of Bern, Bern, Switzerland
| | | | - Gregor Hasler
- Unit of Psychiatry Research, University of Fribourg, Fribourg, Switzerland
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Xu H, Yang F. The interplay of dopamine metabolism abnormalities and mitochondrial defects in the pathogenesis of schizophrenia. Transl Psychiatry 2022; 12:464. [PMID: 36344514 PMCID: PMC9640700 DOI: 10.1038/s41398-022-02233-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/23/2022] [Revised: 10/20/2022] [Accepted: 10/24/2022] [Indexed: 11/09/2022] Open
Abstract
Dopamine (DA) is a major monoamine neurotransmitter in the brain and has essential roles in higher functions of the brain. Malfunctions of dopaminergic signaling have been implicated in various mental disorders such as addiction, attention deficit/hyperactivity disorder, Huntington's disease, Parkinson's disease (PD), and schizophrenia. The pathogenesis of PD and schizophrenia involves the interplay of mitochondrial defect and DA metabolism abnormalities. This article focuses on this issue in schizophrenia. It started with the introduction of metabolism, behavioral action, and physiology of DA, followed by reviewing evidence for malfunctions of dopaminergic signaling in patients with schizophrenia. Then it provided an overview of multiple facets of mitochondrial physiology before summarizing mitochondrial defects reported in clinical studies with schizophrenia patients. Finally, it discussed the interplay between DA metabolism abnormalities and mitochondrial defects and outlined some clinical studies showing effects of combination therapy of antipsychotics and antioxidants in treating patients with schizophrenia. The update and integration of these lines of information may advance our understanding of the etiology, pathogenesis, phenomenology, and treatment of schizophrenia.
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Affiliation(s)
- Haiyun Xu
- School of Mental Health, Wenzhou Medical University, Wenzhou, China.
- Zhejiang Provincial Clinical Research Center for Mental Illness, The Affiliated Kangning Hospital of Wenzhou Medical University, Wenzhou, China.
- Mental Health Center, Shantou University Medical College, Shantou, China.
| | - Fan Yang
- School of Mental Health, Wenzhou Medical University, Wenzhou, China
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Margariti MM, Vlachos II. The concept of psychotic arousal and its relevance to abnormal subjective experiences in schizophrenia. A hypothesis for the formation of primary delusions. Med Hypotheses 2022. [DOI: 10.1016/j.mehy.2022.110915] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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4
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Development of early diagnosis of Parkinson's disease on animal models based on the intranasal administration of α-methyl-p-tyrosine methyl ester in a gel system. Biomed Pharmacother 2022; 150:112944. [PMID: 35405394 DOI: 10.1016/j.biopha.2022.112944] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2022] [Revised: 04/06/2022] [Accepted: 04/06/2022] [Indexed: 11/20/2022] Open
Abstract
The fight against neurodegenerative diseases, including Parkinson's disease (PD), is a global challenge of this century. The effectiveness of current PD therapy is limited, since it is diagnosed many years after the onset, following the death of most nigrostriatal dopaminergic neurons regulating motor function. PD treatment could be greatly improved if it was started at an early (preclinical) stage. For this purpose, it is necessary to develop an early diagnosis of PD, which is the goal of our study. We have developed an early diagnosis of PD on animal models using a provocative test by intranasal administration of α-methyl-p-tyrosine methyl ester (αMPTME), a reversible inhibitor of dopamine synthesis. First, we produced the provocative agent, αMPTME in gel, and showed its safety and penetration into the brain bypassing the blood-brain barrier. Then, the optimal dose of αMPTME and time after administration were selected, at which the level of dopamine in the striatum of intact animals decreases, but does not reach the 30% threshold for the appearance of motor disorders in PD patients. Finally, we proved on animal models that intranasal administration of αMPTME can serve as a diagnostic test for preclinical PD. Indeed, intranasal administration of αMPTME to mice in a model of PD at the preclinical stage reversibly reduced the dopamine level in the striatum to the 30% threshold causing short-term motor disorders. Thus, using animal models of PD, we have developed a provocative test for the preclinical diagnosis of PD, a fundamentally new technology in neurology.
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Caravaggio F, Barnett AJ, Nakajima S, Iwata Y, Kim J, Borlido C, Mar W, Gerretsen P, Remington G, Graff-Guerrero A. The effects of acute dopamine depletion on resting-state functional connectivity in healthy humans. Eur Neuropsychopharmacol 2022; 57:39-49. [PMID: 35091322 DOI: 10.1016/j.euroneuro.2022.01.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Revised: 01/05/2022] [Accepted: 01/10/2022] [Indexed: 11/24/2022]
Abstract
Alpha-methyl-para-tyrosine (AMPT), a competitive inhibitor of tyrosine hydroxylase, can be used to deplete endogenous dopamine in humans. We examined how AMPT-induced dopamine depletion alters resting-state functional connectivity of the basal ganglia, and canonical resting-state networks, in healthy humans. Fourteen healthy participants (8 females; age [mean ± SD] = 27.93 ± 9.86) completed the study. Following dopamine depletion, the caudate showed reduced connectivity with the medial prefrontal cortex (mPFC) (Cohen's d = 1.89, p<.0001). Moreover, the caudate, putamen, globus pallidus, and midbrain all showed reduced connectivity with the occipital cortex (Cohen's d = 1.48-1.90; p<.0001-0.001). Notably, the dorsal caudate showed increased connectivity with the sensorimotor network (Cohen's d = 2.03, p=.002). AMPT significantly decreased self-reported motivation (t(13)=4.19, p=.001) and increased fatigue (t(13)=4.79, p=.0004). A greater increase in fatigue was associated with a greater reduction in connectivity between the substantia nigra and the mPFC (Cohen's d = 3.02, p<.00001), while decreased motivation was correlated with decreased connectivity between the VTA and left sensorimotor cortex (Cohen's d = 2.03, p=.00004). These findings help us to better understand the role of dopamine in basal ganglia function and may help us better understand neuropsychiatric diseases where abnormal dopamine levels are observed.
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Affiliation(s)
- Fernando Caravaggio
- Brain Health Imaging Centre, Centre for Addiction and Mental Health, 250 College Street, Toronto, ON M5T 1R8, Canada; Department of Psychiatry, University of Toronto, 250 College Street, Toronto, ON M5T 1R8, Canada.
| | - Alexander J Barnett
- Center for Neuroscience, University of California, Davis, 1515 Newton Ct, Davis, California 95618, United States of America
| | - Shinichiro Nakajima
- Department of Neuropsychiatry, Keio University, 2 Chome-15-45 Mita, Tokyo 108-8345, Japan
| | - Yusuke Iwata
- Department of Neuropsychiatry, University of Yamanashi, 4 Chome-4-37 Takeda, Kofu 400-8510, Japan
| | - Julia Kim
- Brain Health Imaging Centre, Centre for Addiction and Mental Health, 250 College Street, Toronto, ON M5T 1R8, Canada
| | - Carol Borlido
- Brain Health Imaging Centre, Centre for Addiction and Mental Health, 250 College Street, Toronto, ON M5T 1R8, Canada
| | - Wanna Mar
- Brain Health Imaging Centre, Centre for Addiction and Mental Health, 250 College Street, Toronto, ON M5T 1R8, Canada
| | - Philip Gerretsen
- Brain Health Imaging Centre, Centre for Addiction and Mental Health, 250 College Street, Toronto, ON M5T 1R8, Canada; Department of Psychiatry, University of Toronto, 250 College Street, Toronto, ON M5T 1R8, Canada
| | - Gary Remington
- Brain Health Imaging Centre, Centre for Addiction and Mental Health, 250 College Street, Toronto, ON M5T 1R8, Canada; Department of Psychiatry, University of Toronto, 250 College Street, Toronto, ON M5T 1R8, Canada
| | - Ariel Graff-Guerrero
- Brain Health Imaging Centre, Centre for Addiction and Mental Health, 250 College Street, Toronto, ON M5T 1R8, Canada; Department of Psychiatry, University of Toronto, 250 College Street, Toronto, ON M5T 1R8, Canada
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Lee D, Seo J, Jeong HC, Lee H, Lee SB. The Perspectives of Early Diagnosis of Schizophrenia Through the Detection of Epigenomics-Based Biomarkers in iPSC-Derived Neurons. Front Mol Neurosci 2021; 14:756613. [PMID: 34867186 PMCID: PMC8633873 DOI: 10.3389/fnmol.2021.756613] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2021] [Accepted: 10/20/2021] [Indexed: 12/11/2022] Open
Abstract
The lack of early diagnostic biomarkers for schizophrenia greatly limits treatment options that deliver therapeutic agents to affected cells at a timely manner. While previous schizophrenia biomarker research has identified various biological signals that are correlated with certain diseases, their reliability and practicality as an early diagnostic tool remains unclear. In this article, we discuss the use of atypical epigenetic and/or consequent transcriptional alterations (ETAs) as biomarkers of early-stage schizophrenia. Furthermore, we review the viability of discovering and applying these biomarkers through the use of cutting-edge technologies such as human induced pluripotent stem cell (iPSC)-derived neurons, brain models, and single-cell level analyses.
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Affiliation(s)
- Davin Lee
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology, Daegu, South Korea
| | - Jinsoo Seo
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology, Daegu, South Korea
| | - Hae Chan Jeong
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology, Daegu, South Korea
| | - Hyosang Lee
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology, Daegu, South Korea
| | - Sung Bae Lee
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology, Daegu, South Korea
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McCutcheon RA, Merritt K, Howes OD. Dopamine and glutamate in individuals at high risk for psychosis: a meta-analysis of in vivo imaging findings and their variability compared to controls. World Psychiatry 2021; 20:405-416. [PMID: 34505389 PMCID: PMC8429330 DOI: 10.1002/wps.20893] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Dopaminergic and glutamatergic dysfunction is believed to play a central role in the pathophysiology of schizophrenia. However, it is unclear if abnormalities predate the onset of schizophrenia in individuals at high clinical or genetic risk for the disorder. We systematically reviewed and meta-analyzed studies that have used neuroimaging to investigate dopamine and glutamate function in individuals at increased clinical or genetic risk for psychosis. EMBASE, PsycINFO and Medline were searched form January 1, 1960 to November 26, 2020. Inclusion criteria were molecular imaging measures of striatal presynaptic dopaminergic function, striatal dopamine receptor availability, or glutamate function. Separate meta-analyses were conducted for genetic high-risk and clinical high-risk individuals. We calculated standardized mean differences between high-risk individuals and controls, and investigated whether the variability of these measures differed between the two groups. Forty-eight eligible studies were identified, including 1,288 high-risk individuals and 1,187 controls. Genetic high-risk individuals showed evidence of increased thalamic glutamate + glutamine (Glx) concentrations (Hedges' g=0.36, 95% CI: 0.12-0.61, p=0.003). There were no significant differences between high-risk individuals and controls in striatal presynaptic dopaminergic function, striatal D2/D3 receptor availability, prefrontal cortex glutamate or Glx, hippocampal glutamate or Glx, or basal ganglia Glx. In the meta-analysis of variability, genetic high-risk individuals showed reduced variability of striatal D2/D3 receptor availability compared to controls (log coefficient of variation ratio, CVR=-0.24, 95% CI: -0.46 to -0.02, p=0.03). Meta-regressions of publication year against effect size demonstrated that the magnitude of differences between clinical high-risk individuals and controls in presynaptic dopaminergic function has decreased over time (estimate=-0.06, 95% CI: -0.11 to -0.007, p=0.025). Thus, other than thalamic glutamate concentrations, no neurochemical measures were significantly different between individuals at risk for psychosis and controls. There was also no evidence of increased variability of dopamine or glutamate measures in high-risk individuals compared to controls. Significant heterogeneity, however, exists between studies, which does not allow to rule out the existence of clinically meaningful differences.
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Affiliation(s)
- Robert A McCutcheon
- Department of Psychosis Studies, Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, UK
- Psychiatric Imaging Group, MRC London Institute of Medical Sciences, Hammersmith Hospital, London, UK
- Institute of Clinical Sciences, Faculty of Medicine, Imperial College London, London, UK
- South London and Maudsley NHS Foundation Trust, London, UK
| | - Kate Merritt
- Division of Psychiatry, Institute of Mental Health, University College London, London, UK
| | - Oliver D Howes
- Department of Psychosis Studies, Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, UK
- Psychiatric Imaging Group, MRC London Institute of Medical Sciences, Hammersmith Hospital, London, UK
- Institute of Clinical Sciences, Faculty of Medicine, Imperial College London, London, UK
- South London and Maudsley NHS Foundation Trust, London, UK
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8
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Imaging synaptic dopamine availability in individuals at clinical high-risk for psychosis: a [ 11C]-(+)-PHNO PET with methylphenidate challenge study. Mol Psychiatry 2021; 26:2504-2513. [PMID: 33154566 DOI: 10.1038/s41380-020-00934-w] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Revised: 10/14/2020] [Accepted: 10/22/2020] [Indexed: 02/02/2023]
Abstract
Patients at clinical high-risk (CHR) for psychosis show elevations in [18F]DOPA uptake, an estimate of dopamine (DA) synthesis capacity, in the striatum predictive of conversion to schizophrenia. Intrasynaptic DA levels can be inferred from imaging the change in radiotracer binding at D2 receptors due to a pharmacological challenge. Here, we used methylphenidate, a DA reuptake inhibitor, and [11C]-(+)-PHNO, to measure synaptic DA availability in CHR both in striatal and extra-striatal brain regions. Fourteen unmedicated, nonsubstance using CHR individuals and 14 matched control subjects participated in the study. Subjects underwent two [11C]-(+)-PHNO scans, one at baseline and one following administration of a single oral dose (60 mg) of methylphenidate. [11C]-(+)-PHNO BPND, the binding potential relative to the nondisplaceable compartment, was derived using the simplified reference tissue model with cerebellum as reference tissue. The percent change in BPND between scans, ΔBPND, was computed as an index of synaptic DA availability, and group comparisons were performed with a linear mixed model. An overall trend was found for greater synaptic DA availability (∆BPND) in CHR than controls (p = 0.06). This was driven entirely by ∆BPND in ventral striatum (-34 ± 14% in CHR, -20 ± 12% in HC; p = 0.023). There were no significant group differences in any other brain region. There were no significant differences in DA transmission in any striatal region between converters and nonconverters, although this finding is limited by the small sample size (N = 2). There was a strong and negative correlation between ΔBPND in VST and severity of negative symptoms at baseline in the CHR group (r = -0.66, p < 0.01). We show abnormally increased DA availability in the VST in CHR and an inverse relationship with negative symptoms. Our results suggest a potential early role for mesolimbic dopamine overactivity in CHR. Longitudinal studies are needed to ascertain the significance of the differential topography observed here with the [18F]DOPA literature.
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9
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Andreou C, Borgwardt S. Structural and functional imaging markers for susceptibility to psychosis. Mol Psychiatry 2020; 25:2773-2785. [PMID: 32066828 PMCID: PMC7577836 DOI: 10.1038/s41380-020-0679-7] [Citation(s) in RCA: 50] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/04/2019] [Revised: 01/15/2020] [Accepted: 01/31/2020] [Indexed: 12/21/2022]
Abstract
The introduction of clinical criteria for the operationalization of psychosis high risk provided a basis for early detection and treatment of vulnerable individuals. However, about two-thirds of people meeting clinical high-risk (CHR) criteria will never develop a psychotic disorder. In the effort to increase prognostic precision, structural and functional neuroimaging have received growing attention as a potentially useful resource in the prediction of psychotic transition in CHR patients. The present review summarizes current research on neuroimaging biomarkers in the CHR state, with a particular focus on their prognostic utility and limitations. Large, multimodal/multicenter studies are warranted to address issues important for clinical applicability such as generalizability and replicability, standardization of clinical definitions and neuroimaging methods, and consideration of contextual factors (e.g., age, comorbidity).
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Affiliation(s)
- Christina Andreou
- Department of Psychiatry and Psychotherapy, University of Lübeck, Lübeck, Germany
- Department of Psychiatry (UPK), University of Basel, Basel, Switzerland
| | - Stefan Borgwardt
- Department of Psychiatry and Psychotherapy, University of Lübeck, Lübeck, Germany.
- Department of Psychiatry (UPK), University of Basel, Basel, Switzerland.
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Amphetamine-induced striatal dopamine release in schizotypal personality disorder. Psychopharmacology (Berl) 2020; 237:2649-2659. [PMID: 32572588 DOI: 10.1007/s00213-020-05561-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/23/2019] [Accepted: 05/18/2020] [Indexed: 01/28/2023]
Abstract
RATIONALE Previous research has suggested that schizotypal personality disorder (SPD), a condition that shares clinical and cognitive features with schizophrenia, may be associated with elevated striatal dopamine functioning; however, there are no published studies of dopamine release within subregions of the striatum in SPD. OBJECTIVES To characterize dopamine release capacity in striatal subregions and its relation to clinical and cognitive features in SPD. METHODS We used positron emission tomography with [11C]raclopride and an amphetamine challenge to measure dopamine D2-receptor availability (binding potential, BPND), and its percent change post-amphetamine (∆BPND) to index amphetamine-induced dopamine release, in subregions of the striatum in 16 SPD and 16 healthy control participants. SPD participants were evaluated with measures of schizotypal symptom severity and working memory. RESULTS There were no significant group differences in BPND or ∆BPND in any striatal subregion or whole striatum. Among SPD participants, cognitive-perceptual symptoms were associated at trend level with ∆BPND in the ventral striatum, and disorganized symptoms were significantly negatively related to ∆BPND in several striatal subregions. CONCLUSIONS In contrast to previous findings, SPD was not associated with elevated striatal dopamine release. However, in SPD, there was a moderate positive association between ventral striatal dopamine release and severity of cognitive-perceptual symptoms, and negative associations between striatal dopamine release and severity of disorganized symptoms. Future larger scale investigations that allow for the separate examination of subgroups of participants based on clinical presentation will be valuable in further elucidating striatal DA functioning in SPD.
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Howes OD, Hird EJ, Adams RA, Corlett PR, McGuire P. Aberrant Salience, Information Processing, and Dopaminergic Signaling in People at Clinical High Risk for Psychosis. Biol Psychiatry 2020; 88:304-314. [PMID: 32430200 DOI: 10.1016/j.biopsych.2020.03.012] [Citation(s) in RCA: 53] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Revised: 03/10/2020] [Accepted: 03/10/2020] [Indexed: 01/24/2023]
Abstract
The aberrant salience hypothesis proposes that striatal dopamine dysregulation causes misattribution of salience to irrelevant stimuli leading to psychosis. Recently, new lines of preclinical evidence on information coding by subcortical dopamine coupled with computational models of the brain's ability to predict and make inferences about the world (predictive processing) provide a new perspective on this hypothesis. We review these and summarize the evidence for dopamine dysfunction, reward processing, and salience abnormalities in people at clinical high risk of psychosis (CHR) relative to findings in patients with psychosis. This review identifies consistent evidence for dysregulated subcortical dopamine function in people at CHR, but also indicates a number of areas where neurobiological processes are different in CHR subjects relative to patients with psychosis, particularly in reward processing. We then consider how predictive processing models may explain psychotic symptoms in terms of alterations in prediction error and precision signaling using Bayesian approaches. We also review the potential role of environmental risk factors, particularly early adverse life experiences, in influencing the prior expectations that individuals have about their world in terms of computational models of the progression from being at CHR to frank psychosis. We identify a number of key outstanding questions, including the relative roles of prediction error or precision signaling in the development of symptoms and the mechanism underlying dopamine dysfunction. Finally, we discuss how the integration of computational psychiatry with biological investigation may inform the treatment for people at CHR of psychosis.
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Affiliation(s)
- Oliver D Howes
- Department of Psychosis Studies, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, United Kingdom; National Institute of Health Research Biomedical Research Centre at South London and Maudsley National Health Service Foundation Trust, London, United Kingdom; Medical Research Council London Institute of Medical Sciences, Hammersmith Hospital, London, United Kingdom; Institute of Clinical Sciences, Faculty of Medicine, Imperial College London, London, United Kingdom.
| | - Emily J Hird
- Department of Psychosis Studies, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, United Kingdom; National Institute of Health Research Biomedical Research Centre at South London and Maudsley National Health Service Foundation Trust, London, United Kingdom
| | - Rick A Adams
- Centre for Medical Image Computing, Department of Computer Science, University College London, London, United Kingdom; Max Planck University College London Centre for Computational Psychiatry and Ageing Research, London, United Kingdom
| | - Philip R Corlett
- Department of Psychiatry, Yale School of Medicine, New Haven, Connecticut
| | - Philip McGuire
- Department of Psychosis Studies, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, United Kingdom; National Institute of Health Research Biomedical Research Centre at South London and Maudsley National Health Service Foundation Trust, London, United Kingdom
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Caravaggio F, Iwata Y, Kim J, Shah P, Gerretsen P, Remington G, Graff-Guerrero A. What proportion of striatal D2 receptors are occupied by endogenous dopamine at baseline? A meta-analysis with implications for understanding antipsychotic occupancy. Neuropharmacology 2019; 163:107591. [PMID: 30940535 DOI: 10.1016/j.neuropharm.2019.03.034] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Revised: 03/25/2019] [Accepted: 03/27/2019] [Indexed: 11/30/2022]
Abstract
Using molecular imaging techniques - positron emission tomography (PET) and single-photon emission computed tomography (SPECT) - in conjunction with an acute dopamine depletion challenge (alpha-methyl-para-tyrosine) it is possible to estimate endogenous dopamine levels occupying striatal dopamine D2 receptors (D2R) in humans in vivo. However, it is unclear what proportion of striatal D2R are occupied by endogenous dopamine under normal conditions. This is important since it has been suggested that in schizophrenia there may be a substantial proportion of striatal D2R which are occupied by endogenous dopamine and not accessible by therapeutic doses of antipsychotics. In order to clarify these issues, we conducted a meta-analysis of dopamine depletion studies using substituted benzamide radiotracers in healthy persons. This meta-analysis suggests that anywhere from 8 to 21% (weighted average 11%) of striatal D2R may be occupied by endogenous dopamine at baseline. Using these estimates, we propose an updated occupancy model and tentatively suggest that antipsychotics inhibit a smaller proportion of the total pool of striatal D2R in vivo than previously acknowledged. This article is part of the issue entitled 'Special Issue on Antipsychotics'.
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Affiliation(s)
- Fernando Caravaggio
- Research Imaging Centre, Centre for Addiction and Mental Health, 250 College Street, Toronto, Ontario, M5T 1R8, Canada; Department of Psychiatry, University of Toronto, 250 College Street, Toronto, Ontario, M5T 1R8, Canada.
| | - Yusuke Iwata
- Research Imaging Centre, Centre for Addiction and Mental Health, 250 College Street, Toronto, Ontario, M5T 1R8, Canada; Department of Psychiatry, University of Toronto, 250 College Street, Toronto, Ontario, M5T 1R8, Canada
| | - Julia Kim
- Research Imaging Centre, Centre for Addiction and Mental Health, 250 College Street, Toronto, Ontario, M5T 1R8, Canada; Institute of Medical Science, University of Toronto, 1 Kings College Circle, Toronto, Ontario, M5S 1A8, Canada
| | - Parita Shah
- Research Imaging Centre, Centre for Addiction and Mental Health, 250 College Street, Toronto, Ontario, M5T 1R8, Canada; Institute of Medical Science, University of Toronto, 1 Kings College Circle, Toronto, Ontario, M5S 1A8, Canada
| | - Philip Gerretsen
- Research Imaging Centre, Centre for Addiction and Mental Health, 250 College Street, Toronto, Ontario, M5T 1R8, Canada; Department of Psychiatry, University of Toronto, 250 College Street, Toronto, Ontario, M5T 1R8, Canada; Institute of Medical Science, University of Toronto, 1 Kings College Circle, Toronto, Ontario, M5S 1A8, Canada
| | - Gary Remington
- Research Imaging Centre, Centre for Addiction and Mental Health, 250 College Street, Toronto, Ontario, M5T 1R8, Canada; Department of Psychiatry, University of Toronto, 250 College Street, Toronto, Ontario, M5T 1R8, Canada; Institute of Medical Science, University of Toronto, 1 Kings College Circle, Toronto, Ontario, M5S 1A8, Canada
| | - Ariel Graff-Guerrero
- Research Imaging Centre, Centre for Addiction and Mental Health, 250 College Street, Toronto, Ontario, M5T 1R8, Canada; Department of Psychiatry, University of Toronto, 250 College Street, Toronto, Ontario, M5T 1R8, Canada; Institute of Medical Science, University of Toronto, 1 Kings College Circle, Toronto, Ontario, M5S 1A8, Canada
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Vingerhoets C, Bloemen OJN, Boot E, Bakker G, de Koning MB, da Silva Alves F, Booij J, van Amelsvoort TAMJ. Dopamine in high-risk populations: A comparison of subjects with 22q11.2 deletion syndrome and subjects at ultra high-risk for psychosis. Psychiatry Res Neuroimaging 2018; 272:65-70. [PMID: 29174435 DOI: 10.1016/j.pscychresns.2017.11.014] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/25/2017] [Revised: 10/06/2017] [Accepted: 11/17/2017] [Indexed: 10/18/2022]
Abstract
Striatal dopamine (DA) dysfunction has been consistently reported in psychotic disorders. Differences and similarities in the pathogenesis between populations at clinical and genetic risk for developing psychosis are yet to be established. Here we explored markers of dopamine (DA) function in subjects meeting clinically ultra-high risk criteria for psychosis (UHR) and in subjects with 22q11.2 deletion syndrome (22q11DS), a genetic condition associated with significant risk for developing psychotic disorders. Single Photon Emission Computed Tomography (SPECT) with 123I-labelled iodobenzamide ([123I]IBZM) was used to measure striatal DA D2/3 receptor binding potential (D2R BPND). Also, peripheral DAergic markers were assessed in serum and urine (plasma prolactin (pPRL), plasma homovanillic acid (pHVA) and urine DA(uDA)). No significant difference in striatal D2R BPND was found between UHR and 22q11DS subjects. Compared to UHR subjects, pPRL and pHVA were lower and uDA levels were higher in the 22q11DS subjects. However, after correcting for age and gender, only pPRL as significantly lower in the 22q11DS patients. These results may suggest that there are differences in DAergic markers between subjects with UHR and with 22q11DS that may reflect differences in the pathways to psychosis. However, bigger samples are needed to replicate these findings.
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Affiliation(s)
- Claudia Vingerhoets
- Maastricht University, Department of Psychiatry and Psychology, Maastricht, The Netherlands; Academic Medical Center, Department of Nuclear Medicine, Amsterdam, The Netherlands.
| | - Oswald J N Bloemen
- Maastricht University, Department of Psychiatry and Psychology, Maastricht, The Netherlands; GGZ Centraal, Center for Mental Health Care Innova, Amersfoort, The Netherlands
| | - Erik Boot
- Academic Medical Center, Department of Nuclear Medicine, Amsterdam, The Netherlands; The Dalglish Family 22q Clinic, Toronto, Ontario, Canada
| | - Geor Bakker
- Maastricht University, Department of Psychiatry and Psychology, Maastricht, The Netherlands; Academic Medical Center, Department of Nuclear Medicine, Amsterdam, The Netherlands
| | - Mariken B de Koning
- Academic Medical Center, Department of Psychiatry, Amsterdam, The Netherlands
| | | | - Jan Booij
- Academic Medical Center, Department of Nuclear Medicine, Amsterdam, The Netherlands
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14
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Kesby JP, Eyles DW, McGrath JJ, Scott JG. Dopamine, psychosis and schizophrenia: the widening gap between basic and clinical neuroscience. Transl Psychiatry 2018; 8:30. [PMID: 29382821 PMCID: PMC5802623 DOI: 10.1038/s41398-017-0071-9] [Citation(s) in RCA: 196] [Impact Index Per Article: 32.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/18/2017] [Revised: 10/10/2017] [Accepted: 10/26/2017] [Indexed: 12/18/2022] Open
Abstract
The stagnation in drug development for schizophrenia highlights the need for better translation between basic and clinical research. Understanding the neurobiology of schizophrenia presents substantial challenges but a key feature continues to be the involvement of subcortical dopaminergic dysfunction in those with psychotic symptoms. Our contemporary knowledge regarding dopamine dysfunction has clarified where and when dopaminergic alterations may present in schizophrenia. For example, clinical studies have shown patients with schizophrenia show increased presynaptic dopamine function in the associative striatum, rather than the limbic striatum as previously presumed. Furthermore, subjects deemed at high risk of developing schizophrenia show similar presynaptic dopamine abnormalities in the associative striatum. Thus, our view of subcortical dopamine function in schizophrenia continues to evolve as we accommodate this newly acquired information. However, basic research in animal models has been slow to incorporate these clinical findings. For example, psychostimulant-induced locomotion, the commonly utilised phenotype for positive symptoms in rodents, is heavily associated with dopaminergic activation in the limbic striatum. This anatomical misalignment has brought into question how we assess positive symptoms in animal models and represents an opportunity for improved translation between basic and clinical research. The current review focuses on the role of subcortical dopamine dysfunction in psychosis and schizophrenia. We present and discuss alternative phenotypes that may provide a more translational approach to assess the neurobiology of positive symptoms in schizophrenia. Incorporation of recent clinical findings is essential if we are to develop meaningful translational animal models.
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Affiliation(s)
- JP Kesby
- 0000 0000 9320 7537grid.1003.2Queensland Brain Institute, The University of Queensland, St. Lucia, QLD Australia ,0000 0000 9320 7537grid.1003.2Centre for Clinical Research, Faculty of Medicine, The University of Queensland, Herston, QLD Australia
| | - DW Eyles
- 0000 0000 9320 7537grid.1003.2Queensland Brain Institute, The University of Queensland, St. Lucia, QLD Australia ,0000 0004 0606 3563grid.417162.7Queensland Centre for Mental Health Research, The Park Centre for Mental Health, Wacol, QLD Australia
| | - JJ McGrath
- 0000 0000 9320 7537grid.1003.2Queensland Brain Institute, The University of Queensland, St. Lucia, QLD Australia ,0000 0004 0606 3563grid.417162.7Queensland Centre for Mental Health Research, The Park Centre for Mental Health, Wacol, QLD Australia ,0000 0001 1956 2722grid.7048.bNational Centre for Register-based Research, Aarhus University, Aarhus C, Denmark
| | - JG Scott
- 0000 0000 9320 7537grid.1003.2Centre for Clinical Research, Faculty of Medicine, The University of Queensland, Herston, QLD Australia ,0000 0004 0606 3563grid.417162.7Queensland Centre for Mental Health Research, The Park Centre for Mental Health, Wacol, QLD Australia ,0000 0001 0688 4634grid.416100.2Metro North Mental Health, Royal Brisbane and Women’s Hospital, Herston, QLD Australia
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15
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Jauhar S, Nour MM, Veronese M, Rogdaki M, Bonoldi I, Azis M, Turkheimer F, McGuire P, Young AH, Howes OD. A Test of the Transdiagnostic Dopamine Hypothesis of Psychosis Using Positron Emission Tomographic Imaging in Bipolar Affective Disorder and Schizophrenia. JAMA Psychiatry 2017; 74:1206-1213. [PMID: 29049482 PMCID: PMC6059355 DOI: 10.1001/jamapsychiatry.2017.2943] [Citation(s) in RCA: 131] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
Importance The dopamine hypothesis suggests that dopamine abnormalities underlie psychosis, irrespective of diagnosis, implicating dopamine dysregulation in bipolar affective disorder and schizophrenia, in line with the research domain criteria approach. However, this hypothesis has not been directly examined in individuals diagnosed with bipolar disorder with psychosis. Objectives To test whether dopamine synthesis capacity is elevated in bipolar disorder with psychosis and how this compares with schizophrenia and matched controls and to examine whether dopamine synthesis capacity is associated with psychotic symptom severity, irrespective of diagnostic class. Design, Setting, and Participants This cross-sectional case-control positron emission tomographic study was performed in the setting of first-episode psychosis services in an inner-city area (London, England). Sixty individuals participated in the study (22 with bipolar psychosis [18 antipsychotic naive or free], 16 with schizophrenia [14 antipsychotic naive or free], and 22 matched controls) and underwent fluorodihydroxyphenyl-l-alanine ([18F]-DOPA) positron emission tomography to examine dopamine synthesis capacity. Standardized clinical measures, including the Positive and Negative Syndrome Scale, Young Mania Rating Scale, and Global Assessment of Functioning, were administered. The study dates were March 2013 to November 2016. Main Outcomes and Measures Dopamine synthesis capacity (Kicer) and clinical measures (Positive and Negative Syndrome Scale, Young Mania Rating Scale, and Global Assessment of Functioning). Results The mean (SD) ages of participants were 23.6 (3.6) years in 22 individuals with bipolar psychosis (13 male), 26.3 (4.4) years in 16 individuals with schizophrenia (14 male), and 24.5 (4.5) years in controls (14 male). There was a significant group difference in striatal dopamine synthesis capacity (Kicer) (F2,57 = 6.80, P = .002). Kicer was significantly elevated in both the bipolar group (mean [SD], 13.18 [1.08] × 10-3 min-1; P = .002) and the schizophrenia group (mean [SD], 12.94 [0.79] × 10-3 min-1; P = .04) compared with controls (mean [SD], 12.16 [0.92] × 10-3 min-1). There was no significant difference in striatal Kicer between the bipolar and schizophrenia groups. Kicer was significantly positively correlated with positive psychotic symptom severity in the combined bipolar and schizophrenia sample experiencing a current psychotic episode, explaining 27% of the variance in symptom severity (n = 32, r = 0.52, P = .003). There was a significant positive association between Kicer and positive psychotic symptom severity in individuals with bipolar disorder experiencing a current psychotic episode (n = 16, r = 0.60, P = .01), which remained significant after adjusting for manic symptom severity. Conclusions and Relevance These findings are consistent with a transdiagnostic role for dopamine dysfunction in the pathoetiology of psychosis and suggest dopamine synthesis capacity as a potential novel drug target for bipolar disorder and schizophrenia.
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Affiliation(s)
- Sameer Jauhar
- Department of Psychosis Studies, Institute of Psychiatry, Psychology and Neuroscience, King's College, London, England
- Psychosis Clinical Academic Group, South London and Maudsley National Health Service Foundation Trust, London, England
| | - Matthew M Nour
- Department of Psychosis Studies, Institute of Psychiatry, Psychology and Neuroscience, King's College, London, England
- Medical Research Council London Institute of Medical Sciences, Imperial College, London, England
| | - Mattia Veronese
- Centre for Neuroimaging Studies, Institute of Psychiatry, Psychology and Neuroscience, King's College, London, England
| | - Maria Rogdaki
- Medical Research Council London Institute of Medical Sciences, Imperial College, London, England
| | - Ilaria Bonoldi
- Department of Psychosis Studies, Institute of Psychiatry, Psychology and Neuroscience, King's College, London, England
- Psychosis Clinical Academic Group, South London and Maudsley National Health Service Foundation Trust, London, England
| | - Matilda Azis
- Department of Psychosis Studies, Institute of Psychiatry, Psychology and Neuroscience, King's College, London, England
| | - Federico Turkheimer
- Centre for Neuroimaging Studies, Institute of Psychiatry, Psychology and Neuroscience, King's College, London, England
| | - Philip McGuire
- Department of Psychosis Studies, Institute of Psychiatry, Psychology and Neuroscience, King's College, London, England
- Psychosis Clinical Academic Group, South London and Maudsley National Health Service Foundation Trust, London, England
| | - Allan H Young
- Department of Psychological Medicine, Institute of Psychiatry, Psychology and Neuroscience, King's College, London, England
| | - Oliver D Howes
- Department of Psychosis Studies, Institute of Psychiatry, Psychology and Neuroscience, King's College, London, England
- Psychosis Clinical Academic Group, South London and Maudsley National Health Service Foundation Trust, London, England
- Medical Research Council London Institute of Medical Sciences, Imperial College, London, England
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16
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Howes OD, McCutcheon R, Owen MJ, Murray RM. The Role of Genes, Stress, and Dopamine in the Development of Schizophrenia. Biol Psychiatry 2017; 81:9-20. [PMID: 27720198 PMCID: PMC5675052 DOI: 10.1016/j.biopsych.2016.07.014] [Citation(s) in RCA: 334] [Impact Index Per Article: 47.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/21/2015] [Revised: 07/08/2016] [Accepted: 07/10/2016] [Indexed: 02/06/2023]
Abstract
The dopamine hypothesis is the longest standing pathoetiologic theory of schizophrenia. Because it was initially based on indirect evidence and findings in patients with established schizophrenia, it was unclear what role dopamine played in the onset of the disorder. However, recent studies in people at risk of schizophrenia have found elevated striatal dopamine synthesis capacity and increased dopamine release to stress. Furthermore, striatal dopamine changes have been linked to altered cortical function during cognitive tasks, in line with preclinical evidence that a circuit involving cortical projections to the striatum and midbrain may underlie the striatal dopamine changes. Other studies have shown that a number of environmental risk factors for schizophrenia, such as social isolation and childhood trauma, also affect presynaptic dopaminergic function. Advances in preclinical work and genetics have begun to unravel the molecular architecture linking dopamine, psychosis, and psychosocial stress. Included among the many genes associated with risk of schizophrenia are the gene encoding the dopamine D2 receptor and those involved in the upstream regulation of dopaminergic synthesis, through glutamatergic and gamma-aminobutyric acidergic pathways. A number of these pathways are also linked to the stress response. We review these new lines of evidence and present a model of how genes and environmental factors may sensitize the dopamine system so that it is vulnerable to acute stress, leading to progressive dysregulation and the onset of psychosis. Finally, we consider the implications for rational drug development, in particular regionally selective dopaminergic modulation, and the potential of genetic factors to stratify patients.
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Affiliation(s)
- Oliver D Howes
- Psychosis Studies, King's College London, London, United Kingdom; MRC Clinical Sciences Centre, Imperial College Hammersmith Hospital, London, United Kingdom.
| | - Robert McCutcheon
- Psychosis Studies, King's College London, London, United Kingdom; MRC Clinical Sciences Centre, Imperial College Hammersmith Hospital, London, United Kingdom
| | - Michael J Owen
- MRC Centre for Neuropsychiatric Genetics and Genomics, and Neuroscience and Mental Health Research Institute, Cardiff University, Cardiff, Wales, United Kingdom
| | - Robin M Murray
- Psychosis Studies, King's College London, London, United Kingdom
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17
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Bakker G, Caan MWA, Vingerhoets WAM, da Silva- Alves F, de Koning M, Boot E, Nieman DH, de Haan L, Bloemen OJ, Booij J, van Amelsvoort TAMJ. Cortical Morphology Differences in Subjects at Increased Vulnerability for Developing a Psychotic Disorder: A Comparison between Subjects with Ultra-High Risk and 22q11.2 Deletion Syndrome. PLoS One 2016; 11:e0159928. [PMID: 27828960 PMCID: PMC5102447 DOI: 10.1371/journal.pone.0159928] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2016] [Accepted: 07/11/2016] [Indexed: 01/14/2023] Open
Abstract
Introduction Subjects with 22q11.2 deletion syndrome (22q11DS) and subjects with ultra-high risk for psychosis (UHR) share a risk of approximately 30% to develop a psychotic disorder. Studying these groups helps identify biological markers of pathophysiological processes involved in the development of psychosis. Total cortical surface area (cSA), total cortical grey matter volume (cGMV), cortical thickness (CT), and local gyrification index (LGI) of the cortical structure have a distinct neurodevelopmental origin making them important target markers to study in relation to the development of psychosis. Materials and Methods Structural T1-weighted high resolution images were acquired using a 3 Tesla Intera MRI system in 18 UHR subjects, 18 22q11DS subjects, and 24 matched healthy control (HC) subjects. Total cSA, total cGMV, mean CT, and regional vertex-wise differences in CT and LGI were assessed using FreeSurfer software. The Positive and Negative Syndrome Scale was used to assess psychotic symptom severity in UHR and 22q11DS subjects at time of scanning. Results 22q11DS subjects had lower total cSA and total cGMV compared to UHR and HC subjects. The 22q11DS subjects showed bilateral lower LGI in the i) prefrontal cortex, ii) precuneus, iii) precentral gyrus and iv) cuneus compared to UHR subjects. Additionally, lower LGI was found in the left i) fusiform gyrus and right i) pars opercularis, ii) superior, and iii) inferior temporal gyrus in 22q11DS subjects compared to HC. In comparison to 22q11DS subjects, the UHR subjects had lower CT of the insula. For both risk groups, positive symptom severity was negatively correlated to rostral middle frontal gyrus CT. Conclusion A shared negative correlation between positive symptom severity and rostral middle frontal gyrus CT in UHR and 22q11DS may be related to their increased vulnerability to develop a psychotic disorder. 22q11DS subjects were characterised by widespread lower degree of cortical gyrification linked to early and postnatal neurodevelopmental pathology. No implications for early neurodevelopmental pathology were found for the UHR subjects, although they did have distinctively lower insula CT which may have arisen from defective pruning processes during adolescence. Implications of these findings in relation to development of psychotic disorders are in need of further investigation in longitudinal studies.
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Affiliation(s)
- Geor Bakker
- Department of Psychiatry & Psychology, University of Maastricht, Maastricht, The Netherlands
- Department of Nuclear Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
- * E-mail:
| | - Matthan W. A. Caan
- Department of Radiology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Wilhelmina A. M. Vingerhoets
- Department of Psychiatry & Psychology, University of Maastricht, Maastricht, The Netherlands
- Department of Nuclear Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Fabiana da Silva- Alves
- Department of Nuclear Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | | | - Erik Boot
- Department of Nuclear Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
- The Dalglish Family 22q Clinic, Toronto, Ontario, Canada
| | - Dorien H. Nieman
- Department of Psychiatry, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Lieuwe de Haan
- Department of Psychiatry, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
- Arkin Mental Health Care, Amsterdam, The Netherlands
| | - Oswald J. Bloemen
- Department of Psychiatry & Psychology, University of Maastricht, Maastricht, The Netherlands
- GGZ Centraal, Center for Mental Health Care Innova, Amersfoort, The Netherlands
| | - Jan Booij
- Department of Nuclear Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Thérèse A. M. J. van Amelsvoort
- Department of Psychiatry & Psychology, University of Maastricht, Maastricht, The Netherlands
- Department of Nuclear Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
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18
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Caravaggio F, Kegeles LS, Wilson AA, Remington G, Borlido C, Mamo DC, Graff-Guerrero A. Estimating the effect of endogenous dopamine on baseline [(11) C]-(+)-PHNO binding in the human brain. Synapse 2016; 70:453-60. [PMID: 27341789 DOI: 10.1002/syn.21920] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2016] [Revised: 06/03/2016] [Accepted: 06/20/2016] [Indexed: 11/10/2022]
Abstract
Endogenous dopamine (DA) levels at dopamine D2/3 receptors (D2/3 R) have been quantified in the living human brain using the agonist radiotracer [(11) C]-(+)-PHNO. As an agonist radiotracer, [(11) C]-(+)-PHNO is more sensitive to endogenous DA levels than antagonist radiotracers. We sought to determine the proportion of the variance in baseline [(11) C]-(+)-PHNO binding to D2/3 Rs which can be accounted for by variation in endogenous DA levels. This was done by computing the Pearson's coefficient for the correlation between baseline binding potential (BPND ) and the change in BPND after acute DA depletion, using previously published data. All correlations were inverse, and the proportion of the variance in baseline [(11) C]-(+)-PHNO BPND that can be accounted for by variation in endogenous DA levels across the striatal subregions ranged from 42-59%. These results indicate that lower baseline values of [(11) C]-(+)-PHNO BPND reflect greater stimulation by endogenous DA. To further validate this interpretation, we sought to examine whether these data could be used to estimate the dissociation constant (Kd) of DA at D2/3 R. In line with previous in vitro work, we estimated the in vivo Kd of DA to be around 20 nM. In summary, the agonist radiotracer [(11) C]-(+)-PHNO can detect the impact of endogenous DA levels at D2/3 R in the living human brain from a single baseline scan, and may be more sensitive to this impact than other commonly employed radiotracers.
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Affiliation(s)
- Fernando Caravaggio
- Centre for Addiction and Mental Health, Research Imaging Centre, Toronto, Ontario, M5T 1R8, Canada.,Institute of Medical Science, University of Toronto, Toronto, Ontario, M5S 1A8, Canada
| | - Lawrence S Kegeles
- Department of Psychiatry and Radiology, Columbia University College of Physicians and Surgeons, New York State Psychiatric Institute, New York
| | - Alan A Wilson
- Centre for Addiction and Mental Health, Research Imaging Centre, Toronto, Ontario, M5T 1R8, Canada.,Institute of Medical Science, University of Toronto, Toronto, Ontario, M5S 1A8, Canada.,Department of Psychiatry, University of Toronto, Ontario, M5T 1R8, Canada
| | - Gary Remington
- Centre for Addiction and Mental Health, Research Imaging Centre, Toronto, Ontario, M5T 1R8, Canada.,Institute of Medical Science, University of Toronto, Toronto, Ontario, M5S 1A8, Canada.,Department of Psychiatry, University of Toronto, Ontario, M5T 1R8, Canada
| | - Carol Borlido
- Centre for Addiction and Mental Health, Research Imaging Centre, Toronto, Ontario, M5T 1R8, Canada
| | - David C Mamo
- Department of Psychiatry, Faculties of Medicine and Health Science, University of Malta, Msida, Malta
| | - Ariel Graff-Guerrero
- Centre for Addiction and Mental Health, Research Imaging Centre, Toronto, Ontario, M5T 1R8, Canada. .,Institute of Medical Science, University of Toronto, Toronto, Ontario, M5S 1A8, Canada. .,Department of Psychiatry, University of Toronto, Ontario, M5T 1R8, Canada.
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Prolactin concentrations in antipsychotic-naïve patients with schizophrenia and related disorders: A meta-analysis. Schizophr Res 2016; 174:156-160. [PMID: 27068570 DOI: 10.1016/j.schres.2016.03.018] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Revised: 03/14/2016] [Accepted: 03/16/2016] [Indexed: 11/21/2022]
Abstract
OBJECTIVE The use of dopaminergic antagonist antipsychotics is associated with hyperprolactinemia, but some studies have found increased prolactin concentrations in antipsychotic-naive patients with schizophrenia and related disorders. We conducted a systematic review and meta-analysis of studies of prolactin in antipsychotic-naïve patient with these disorders (PRISMA No. CRD42015016337). DATA SOURCES PubMed (Medline), PsycInfo, and Web of Science were searched for articles from 1950 to the present in English. STUDY SELECTION Seven studies of males (N=141 for patients, N=191 for control subjects) and five studies of females (N=67 and N=116) met criteria for inclusion: data on blood prolactin concentrations for both control subjects and antipsychotic-naive patients with schizophrenia or a related disorder, with data available separately for males and females. DATA EXTRACTION Data was extracted from the papers by one author and independently verified by a second. RESULTS The mean effect size for males was 1.02 (95% CI, 0.77, 1.26; p<0.001) and 0.43 for females (95% CI 0.11, 0.76; p<0.01). Meta-regression analyses for age, smoking, body mass index (BMI), year of publication, and cortisol were not significant. Funnel plots did not suggest the presence of a publication bias. CONCLUSIONS Our meta-analyses found significantly increased prolactin levels in both male and female antipsychotic-naïve patients with schizophrenia and related disorders. The small number of studies and limited matching for potentially confounding variables in some of the studies were limitations of this analysis. Prolonged hyperprolactinemia may lead to sexual dysfunction and osteoporosis, and some antipsychotics cause additional elevation of prolactin concentrations.
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Abstract
Despite a lack of recent progress in the treatment of schizophrenia, our understanding of its genetic and environmental causes has considerably improved, and their relationship to aberrant patterns of neurodevelopment has become clearer. This raises the possibility that 'disease-modifying' strategies could alter the course to - and of - this debilitating disorder, rather than simply alleviating symptoms. A promising window for course-altering intervention is around the time of the first episode of psychosis, especially in young people at risk of transition to schizophrenia. Indeed, studies performed in both individuals at risk of developing schizophrenia and rodent models for schizophrenia suggest that pre-diagnostic pharmacotherapy and psychosocial or cognitive-behavioural interventions can delay or moderate the emergence of psychosis. Of particular interest are 'hybrid' strategies that both relieve presenting symptoms and reduce the risk of transition to schizophrenia or another psychiatric disorder. This Review aims to provide a broad-based consideration of the challenges and opportunities inherent in efforts to alter the course of schizophrenia.
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21
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Hong SB, Lee TY, Kwak YB, Kim SN, Kwon JS. Baseline putamen volume as a predictor of positive symptom reduction in patients at clinical high risk for psychosis: A preliminary study. Schizophr Res 2015; 169:178-185. [PMID: 26527246 DOI: 10.1016/j.schres.2015.10.029] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/22/2015] [Revised: 10/13/2015] [Accepted: 10/20/2015] [Indexed: 12/20/2022]
Abstract
OBJECTIVES Illness course in individuals at clinical high risk (CHR) status for psychosis is heterogeneous, which limits effective treatment for all CHR subgroups. Baseline predictors of positive symptom trajectory in the CHR group will reduce such limitations. We singled out the putamen, thought to be involved in the generation of the key schizophrenia symptoms early in the course of disease, as a potential predictor of positive symptom trajectory in CHR patients. METHOD We recruited 45 CHR patients and 29 age- and gender-matched healthy controls (HC). The CHR group was divided into patients with positive symptom reduction (CHR-R) and patients without positive symptom reduction (CHR-NR) at 6 months. Comparisons were made between the baseline putamen volumes of CHR-R, CHR-NR and HC groups. The relationship between baseline putamen volumes and clinical measures was investigated. RESULTS Left putamen volumes of CHR-R patients were significantly smaller than those of HCs (p=0.002) and of CHR-NR patients (p=0.024). CHR-R patients had significantly reduced leftward laterality compared to HCs (p=0.007). In the CHR-R group, bilateral putamen volumes were correlated with positive symptom severity at baseline (r=-0.552, p=0.001) and at 6 months (r=-0.360, p=0.043), and predicted positive symptom score change in 6 months at a trend level (p=0.092). CONCLUSION Smaller left putamen volumes in CHR-R patients, and the correlation between positive symptom severity and putamen volumes suggest that putamen volume is a possible risk-stratifier and predictor of clinical course in the CHR population.
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Affiliation(s)
- Sang Bin Hong
- Department of Psychiatry, Seoul National University College of Medicine, Seoul, Republic of Korea
| | - Tae Young Lee
- Department of Psychiatry, Seoul National University College of Medicine, Seoul, Republic of Korea; Medical Research Center, Seoul National University College of Medicine, Seoul, Republic of Korea.
| | - Yoo Bin Kwak
- Department of Brain & Cognitive Sciences, Seoul National University College of National Sciences, Seoul, Republic of Korea
| | - Sung Nyun Kim
- Department of Psychiatry, Seoul National University College of Medicine, Seoul, Republic of Korea
| | - Jun Soo Kwon
- Department of Psychiatry, Seoul National University College of Medicine, Seoul, Republic of Korea; Medical Research Center, Seoul National University College of Medicine, Seoul, Republic of Korea; Department of Brain & Cognitive Sciences, Seoul National University College of National Sciences, Seoul, Republic of Korea
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Abstract
The glutamate and dopamine hypotheses are leading theories of the pathoaetiology of schizophrenia. Both were initially based on indirect evidence from pharmacological studies supported by post-mortem findings, but have since been substantially advanced by new lines of evidence from in vivo imaging studies. This review provides an update on the latest findings on dopamine and glutamate abnormalities in schizophrenia, focusing on in vivo neuroimaging studies in patients and clinical high-risk groups, and considers their implications for understanding the biology and treatment of schizophrenia. These findings have refined both the dopamine and glutamate hypotheses, enabling greater anatomical and functional specificity, and have been complemented by preclinical evidence showing how the risk factors for schizophrenia impact on the dopamine and glutamate systems. The implications of this new evidence for understanding the development and treatment of schizophrenia are considered, and the gaps in current knowledge highlighted. Finally, the evidence for an integrated model of the interactions between the glutamate and dopamine systems is reviewed, and future directions discussed.
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Affiliation(s)
- Oliver Howes
- Psychiatric Imaging, MRC Clinical Sciences Centre, Hammersmith Hospital, London, UK Institute of Psychiatry, King's College London, London, UK
| | - Rob McCutcheon
- Psychiatric Imaging, MRC Clinical Sciences Centre, Hammersmith Hospital, London, UK Institute of Psychiatry, King's College London, London, UK
| | - James Stone
- Psychiatric Imaging, MRC Clinical Sciences Centre, Hammersmith Hospital, London, UK Institute of Psychiatry, King's College London, London, UK
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23
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Kahn RS, Sommer IE. The neurobiology and treatment of first-episode schizophrenia. Mol Psychiatry 2015; 20:84-97. [PMID: 25048005 PMCID: PMC4320288 DOI: 10.1038/mp.2014.66] [Citation(s) in RCA: 151] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/11/2014] [Revised: 04/15/2014] [Accepted: 05/12/2014] [Indexed: 12/26/2022]
Abstract
It is evident that once psychosis is present in patients with schizophrenia, the underlying biological process of the illness has already been ongoing for many years. At the time of diagnosis, patients with schizophrenia show decreased mean intracranial volume (ICV) as compared with healthy subjects. Since ICV is driven by brain growth, which reaches its maximum size at approximately 13 years of age, this finding suggests that brain development in patients with schizophrenia is stunted before that age. The smaller brain volume is expressed as decrements in both grey and white matter. After diagnosis, it is mainly the grey matter loss that progresses over time whereas white matter deficits are stable or may even improve over the course of the illness. To understand the possible causes of the brain changes in the first phase of schizophrenia, evidence from treatment studies, postmortem and neuroimaging investigations together with animal experiments needs to be incorporated. These data suggest that the pathophysiology of schizophrenia is multifactorial. Increased striatal dopamine synthesis is already evident before the time of diagnosis, starting during the at-risk mental state, and increases during the onset of frank psychosis. Cognitive impairment and negative symptoms may, in turn, result from other abnormalities, such as NMDA receptor hypofunction and low-grade inflammation of the brain. The latter two dysfunctions probably antedate increased dopamine synthesis by many years, reflecting the much earlier presence of cognitive and social dysfunction. Although correction of the hyperdopaminergic state with antipsychotic agents is generally effective in patients with a first-episode psychosis, the effects of treatments to correct NMDA receptor hypofunction or low-grade inflammation are (so far) rather modest at best. Improved efficacy of these interventions can be expected when they are applied at the onset of cognitive and social dysfunction, rather than at the onset of psychosis.
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Affiliation(s)
- R S Kahn
- Department of Psychiatry, Brain Center Rudolf Magnus, University Medical Centre Utrecht, Utrecht, The Netherlands
| | - I E Sommer
- Department of Psychiatry, Brain Center Rudolf Magnus, University Medical Centre Utrecht, Utrecht, The Netherlands
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Caravaggio F, Nakajima S, Borlido C, Remington G, Gerretsen P, Wilson A, Houle S, Menon M, Mamo D, Graff-Guerrero A. Estimating endogenous dopamine levels at D2 and D3 receptors in humans using the agonist radiotracer [(11)C]-(+)-PHNO. Neuropsychopharmacology 2014; 39:2769-76. [PMID: 24874713 PMCID: PMC4200487 DOI: 10.1038/npp.2014.125] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/14/2014] [Revised: 04/15/2014] [Accepted: 05/05/2014] [Indexed: 11/10/2022]
Abstract
Using positron emission tomography (PET) and an acute dopamine depletion challenge it is possible to estimate endogenous dopamine levels occupying dopamine D2/3 receptors (D2/3R) in humans in vivo. Our group has developed [(11)C]-(+)-PHNO, the first agonist radiotracer with preferential in vivo affinity for D3R. Thus, the use of [(11)C]-(+)-PHNO offers the novel possibility of (i) estimating in vivo endogenous dopamine levels at D2/3R using an agonist radiotracer, and (ii) estimating endogenous dopamine levels at D3R in extrastriatal regions such as the substantia nigra, hypothalamus, and ventral pallidum. Ten healthy participants underwent a [(11)C]-(+)-PHNO PET scan under baseline conditions and another under acute endogenous dopamine depletion achieved via oral administration of alpha-methyl-para-tyrosine (64 mg/kg). [(11)C]-(+)-PHNO binding was sensitive to acute dopamine depletion, allowing in vivo estimates of endogenous dopamine in D2R-rich regions (caudate and putamen), mixed D2/3R-rich regions (ventral striatum and globus pallidus), and extrastriatal D3R-rich regions (hypothalamus and ventral pallidum). Dopamine depletion decreased self-reported vigor, which was correlated with the reduction in dopamine levels in the globus pallidus. [(11)C]-(+)-PHNO is a suitable radiotracer for use in estimating endogenous dopamine levels at D2R and D3R in neuropsychiatric populations.
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Affiliation(s)
- Fernando Caravaggio
- Research Imaging Centre, Centre for Addiction and Mental Health, Toronto, ON, Canada,Institute of Medical Science, University of Toronto, Toronto, ON, Canada
| | - Shinichiro Nakajima
- Research Imaging Centre, Centre for Addiction and Mental Health, Toronto, ON, Canada,Department of Psychiatry, University of Toronto, Toronto, ON, Canada
| | - Carol Borlido
- Research Imaging Centre, Centre for Addiction and Mental Health, Toronto, ON, Canada
| | - Gary Remington
- Research Imaging Centre, Centre for Addiction and Mental Health, Toronto, ON, Canada,Institute of Medical Science, University of Toronto, Toronto, ON, Canada,Department of Psychiatry, University of Toronto, Toronto, ON, Canada
| | - Philip Gerretsen
- Research Imaging Centre, Centre for Addiction and Mental Health, Toronto, ON, Canada,Institute of Medical Science, University of Toronto, Toronto, ON, Canada,Department of Psychiatry, University of Toronto, Toronto, ON, Canada
| | - Alan Wilson
- Research Imaging Centre, Centre for Addiction and Mental Health, Toronto, ON, Canada,Institute of Medical Science, University of Toronto, Toronto, ON, Canada,Department of Psychiatry, University of Toronto, Toronto, ON, Canada
| | - Sylvain Houle
- Research Imaging Centre, Centre for Addiction and Mental Health, Toronto, ON, Canada,Department of Psychiatry, University of Toronto, Toronto, ON, Canada
| | - Mahesh Menon
- Research Imaging Centre, Centre for Addiction and Mental Health, Toronto, ON, Canada,Department of Psychiatry, University of Toronto, Toronto, ON, Canada
| | - David Mamo
- Research Imaging Centre, Centre for Addiction and Mental Health, Toronto, ON, Canada,Department of Psychiatry, University of Toronto, Toronto, ON, Canada
| | - Ariel Graff-Guerrero
- Research Imaging Centre, Centre for Addiction and Mental Health, Toronto, ON, Canada,Institute of Medical Science, University of Toronto, Toronto, ON, Canada,Department of Psychiatry, University of Toronto, Toronto, ON, Canada,Research Imaging Centre, Centre for Addiction and Mental Health, 250 College Street, Toronto, ON, Canada M5T 1R8. Tel: +416 535 8501x4834, Fax: +1 416 979 3855, E-mail:
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25
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Bonoldi I, Howes OD. Presynaptic dopaminergic function: implications for understanding treatment response in psychosis. CNS Drugs 2014; 28:649-63. [PMID: 24919790 DOI: 10.1007/s40263-014-0177-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
All current antipsychotic drugs block dopamine (DA) receptors, but the nature of the DA dysfunction in schizophrenia has not been clear. However, consistent evidence now shows that presynaptic dopaminergic function is altered in schizophrenia, specifically in terms of increased DA synthesis capacity, baseline synaptic DA levels, and DA release. Furthermore, presynaptic dopaminergic function is already elevated in prodromal patients who later developed the disorder. Currently available antipsychotics act on postsynaptic receptors, not targeting presynaptic DA abnormalities. This has implications for understanding response and developing new treatments. The lack of normalization of the abnormal presynaptic function could explain why discontinuation is likely to lead to relapse, because the major dopaminergic function persists, meaning that once treatment stops there is nothing to oppose the dysregulated dopamine function reinstating symptoms. Furthermore, it suggests that drugs that target presynaptic dopaminergic function may constitute new treatment possibilities for schizophrenic patients, in particular, for those in whom antipsychotics are poorly effective. In addition, the longitudinal changes with the onset of psychosis indicate the potential to target a defined dynamic neurochemical abnormality to prevent the onset of psychosis.
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Affiliation(s)
- I Bonoldi
- Department of Psychosis Studies, Institute of Psychiatry, King's College of London, De Crespigny Park 16, London, SE5 8AF, UK,
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26
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De Koning MB, Bloemen OJ, Van Duin EDA, Booij J, Abel KM, De Haan L, Linszen DH, Van Amelsvoort TA. Pre-pulse inhibition and striatal dopamine in subjects at an ultra-high risk for psychosis. J Psychopharmacol 2014; 28:553-60. [PMID: 24526133 DOI: 10.1177/0269881113519507] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Reduced prepulse inhibition (PPI) of the acoustic startle response is thought to represent a robust biomarker in schizophrenia. Reduced PPI has been demonstrated in subjects at ultra high risk (UHR) for developing psychosis. Imaging studies report disruption of striatal dopaminergic neurotransmission in patients with schizophrenia. First, we compared the PPI of the acoustic startle response in UHR subjects versus healthy controls, to see if we could replicate previous findings of reduced PPI; secondly, we investigated our hypothesis that PPI would be negatively correlated with striatal synaptic dopamine (DA) concentration. We measured the startle reactivity and PPI of the acoustic startle response in 14 UHR subjects, and 14 age- and gender-matched healthy controls. Imaging of 11 UHR subjects and 11 healthy controls was completed by an [(123)I]-IBZM (radiotracer for dopamine D2/3 receptors) SPECT, at baseline and again after DA depletion with alpha-methyl-para-tyrosine (AMPT). The percentage change in striatal [(123)I]-IBZM radiotracer binding potential is a proxy of striatal synaptic DA concentration. UHR subjects showed reduced PPI, compared to control subjects. In both UHR and control subjects, there were no significant correlations between striatal synaptic DA concentration and PPI. We provide further evidence for the hypothesis that these two biomarkers are measuring different aspects of pathophysiology.
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Affiliation(s)
- Mariken B De Koning
- Department of Psychiatry, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands Arkin Mental Health Care, Amsterdam, The Netherlands
| | - Oswald Jn Bloemen
- Department of Psychiatry, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands
| | - Esther DA Van Duin
- Department of Psychiatry, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands
| | - Jan Booij
- Department of Nuclear Medicine, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands
| | - Kathryn M Abel
- Centre for Women's Mental Health, Manchester Academy of Health Sciences, University of Manchester, Manchester, UK
| | - Lieuwe De Haan
- Department of Psychiatry, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands
| | - Don H Linszen
- Department of Psychiatry, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands
| | - Thérèse Amj Van Amelsvoort
- Department of Psychiatry, Maastricht University, Maastricht, The Netherlands Department of Psychiatry, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands
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Seeman P. Schizophrenia and dopamine receptors. Eur Neuropsychopharmacol 2013; 23:999-1009. [PMID: 23860356 DOI: 10.1016/j.euroneuro.2013.06.005] [Citation(s) in RCA: 82] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/07/2012] [Revised: 04/06/2013] [Accepted: 06/24/2013] [Indexed: 02/06/2023]
Abstract
Schizophrenia patients are behaviorally supersensitive to dopamine-like drugs such as amphetamine or methylphenidate, meaning that patients respond to such drugs with increased psychotic symptoms, as compared to control subjects. A basis of such supersensitivity may be an increased pre-synaptic release of dopamine or a post-synaptic elevation of D2 receptors or of D2High receptors in active stages of schizophrenia. While the pre-synaptic release of dopamine is normal in stable patients with schizophrenia, brain imaging studies find that D2 receptors are increased by an average of 5.8% in antipsychotic-free schizophrenia patients. It is possible that the behavioral supersensitivity may stem from more D2High receptors in schizophrenia. Although the antipsychotic/dopamine D2 receptor can exist in vitro in a state of high affinity for dopamine (as D2High), or in a state of low affinity for dopamine (as D2Low), there is no clear evidence that D2High states can be selectively labeled or stably exist in vivo. Nevertheless, two studies revealed an 80% increase in apparent D2High receptors in schizophrenia patients after reducing endogenous dopamine. The elevation in apparent D2High receptors in vivo in schizophrenia matches the elevation in D2High receptors in vitro in animal models of psychosis, including dopamine-supersensitive animals pretreated with amphetamine, marijuana, or phencyclidine, or animals with gene knockouts in various neurotransmitter pathways, including those for glutamate receptors. The elevation of D2High receptors in vitro and the increased apparent D2High receptors in vivo is consistent with behavioral dopamine supersensitivity in schizophrenia patients.
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Affiliation(s)
- Philip Seeman
- Department of Psychiatry, University of Toronto, 260 Heath Street, West, Unit 605, Toronto, Ont., Canada M5P 3L6; Department of Pharmacology, University of Toronto, 260 Heath Street, West, Unit 605, Toronto, Ont., Canada M5P 3L6.
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28
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Bonoldi I, Howes O. The Enduring Centrality of Dopamine in the Pathophysiology of Schizophrenia. A NEW ERA OF CATECHOLAMINES IN THE LABORATORY AND CLINIC 2013; 68:199-220. [DOI: 10.1016/b978-0-12-411512-5.00010-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/06/2022]
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