Sho Moriguchi

Estimated dopamine D2 receptor occupancy and remission in schizophrenia : analysis of the CATIE data

Abstract In treating schizophrenia, 65% to 80% occupancy of dopamine D2 receptors optimizes therapeutic efficacy while minimizing risks of extrapyramidal symptoms and cognitive impairments. However, it is unclear as to whether it is necessary to keep D2 receptor occupancy within this therapeutic window to maintain clinical response. The data set from phase 1 of the Clinical Antipsychotic Trials in Intervention Effectiveness (CATIE) trial was reappraised. Thirty patients receiving risperidone (12 patients), olanzapine (12 patients), or ziprasidone (6 patients) fulfilled the following definition of remission and were included: a score of 3 or less on the 8 specific items in the Positive and Negative Syndrome Scale (ie, P1, P2, P3, N1, N4, N6, G5, and G9; adopted from Andreasen et al, 2005) at the initial assessment and months 1, 2, and 6. Peak and trough D2 receptor occupancy levels at month 6 were estimated from plasma antipsychotic concentrations using population pharmacokinetic analysis and our D2 prediction model. Estimated mean ± SD peak and trough D2 receptor occupancy levels at month 6 were 70.3% ± 9.8% and 60.5% ± 20.2%, respectively; among these individuals, 46.7% (14 patients) did not achieve continuous blockade of 65% or greater (ie, trough D2 occupancy of <65%). In conclusion, approximately half of patients with remission did not achieve continuous blockade of estimated D2 receptor occupancy 5% or greater. These results extend our previous findings and suggest that sustained D2 receptor occupancy greater than 65% may not always be necessary for the maintenance treatment of schizophrenia.

Revisiting the concept of late catatonia

AIM The objective of this paper is to introduce the concept of late catatonia to foreign readers for the first time in English. METHODS The original study was conducted about 20 years ago. The subjects were 16 persons who first visited our institutions between 1990 and 1996. They fulfilled the following criteria: 1) late-onset psychosis, with the initial mental changes occurring after 40 years of age; 2) more than one catatonic symptom observed during the clinical course; 3) a total clinical course lasting more than 2 years; and 4) no evidence of apparent organic brain disease. The medical records of individual patients were retrospectively reviewed to summarize the clinical features of this diagnosis. RESULTS The crucial feature was the evolution or longitudinal change in the clinical picture over time, with the clinical course being divided into five stages: stage I (prodromal depression), stage II (anxiety and agitation), stage III (hallucination and delusion), stage IV (catatonia syndrome), and residual state. As for treatment, the effect of psychotropic agents was very limited. The electroconvulsive treatment was the most effective treatment option. CONCLUSION Apart from the current diagnostic dichotomy of schizophrenia and mood disorder, the concept of late catatonia is useful in clinical settings and may provide clinically important knowledge.

Occupancy of Norepinephrine Transporter by Duloxetine in Human Brains Measured by Positron Emission Tomography with (S,S)-[18F]FMeNER-D2

Abstract Background The norepinephrine transporter in the brain has been targeted in the treatment of psychiatric disorders. Duloxetine is a serotonin and norepinephrine reuptake inhibitor that has been widely used for the treatment of depression. However, the relationship between dose and plasma concentration of duloxetine and norepinephrine transporter occupancy in the human brain has not been determined. In this study, we examined norepinephrine transporter occupancy by different doses of duloxetine. Methods We calculated norepinephrine transporter occupancies from 2 positron emission tomography scans using (S,S)-[18F]FMeNER-D2 before and after a single oral dose of duloxetine (20 mg, n = 3; 40 mg, n = 3; 60 mg, n =2). Positron emission tomography scans were performed from 120 to 180 minutes after an i.v. bolus injection of (S,S)-[18F]FMeNER-D2. Venous blood samples were taken to measure the plasma concentration of duloxetine just before and after the second positron emission tomography scan. Results Norepinephrine transporter occupancy by duloxetine was 29.7% at 20 mg, 30.5% at 40 mg, and 40.0% at 60 mg. The estimated dose of duloxetine inducing 50% norepinephrine transporter occupancy was 76.8 mg, and the estimated plasma drug concentration inducing 50% norepinephrine transporter occupancy was 58.0 ng/mL. Conclusions Norepinephrine transporter occupancy by clinical doses of duloxetine was approximately 30% to 40% in human brain as estimated using positron emission tomography with (S,S)-[18F]FMeNER-D2.

Affinity States of Striatal Dopamine D2 Receptors in Antipsychotic-Free Patients with Schizophrenia

Abstract Background Dopamine D2 receptors are reported to have high-affinity (D2High) and low-affinity (D2Low) states. Although an increased proportion of D2High has been demonstrated in animal models of schizophrenia, few clinical studies have investigated this alteration of D2High in schizophrenia in vivo. Methods Eleven patients with schizophrenia, including 10 antipsychotic-naive and 1 antipsychotic-free individuals, and 17 healthy controls were investigated. Psychopathology was assessed by Positive and Negative Syndrome Scale, and a 5-factor model was used. Two radioligands, [11C]raclopride and [11C]MNPA, were employed to quantify total dopamine D2 receptor and D2High, respectively, in the striatum by measuring their binding potentials. Binding potential values of [11C]raclopride and [11C]MNPA and the binding potential ratio of [11C]MNPA to [11C]raclopride in the striatal subregions were statistically compared between the 2 diagnostic groups using multivariate analysis of covariance controlling for age, gender, and smoking. Correlations between binding potential and Positive and Negative Syndrome Scale scores were also examined. Results Multivariate analysis of covariance demonstrated a significant effect of diagnosis (schizophrenia and control) on the binding potential ratio (P=.018), although the effects of diagnosis on binding potential values obtained with either [11C]raclopride or [11C]MNPA were nonsignificant. Posthoc test showed that the binding potential ratio was significantly higher in the putamen of patients (P=.017). The Positive and Negative Syndrome Scale “depressed” factor in patients was positively correlated with binding potential values of both ligands in the caudate. Conclusions The present study indicates the possibilities of: (1) a higher proportion of D2High in the putamen despite unaltered amounts of total dopamine D2 receptors; and (2) associations between depressive symptoms and amounts of caudate dopamine D2 receptors in patients with schizophrenia.

Anatomical relationships between serotonin 5-HT2A and dopamine D2 receptors in living human brain

Serotonin 2A (5-HT2A) receptors and dopamine D2 receptors are intimately related to the physiology and pathophysiology of neuropsychiatric disorders. A large number of studies have reported the effectiveness of psychotropic agents targeting 5-HT2A and D2 receptors in these disorders. In addition to the individual functions of these receptors, the interaction between the two neurotransmitter systems has been studied in the living brain. However, little is known about their regional relationship in individual human brains. We investigated regional relationships between 5-HT2A and D2 receptors using positron emission tomography (PET) and a bicluster analysis of the correlation matrix of individual variation in the two receptor densities to identify groups of distinctive regional correlations between the two receptors. Methods Seven healthy volunteers underwent PET scans with [18F]altanserin and [11C]FLB 457 for 5-HT2A and D2 receptors, respectively. As a measure of receptor density, a binding potential (BP) was calculated from PET data for 76 cerebral cortical regions. A correlation matrix was calculated between the binding potentials of [18F]altanserin and [11C]FLB 457 for those regions. The regional relationships were investigated using a bicluster analysis of the correlation matrix with an iterative signature algorithm. Results We identified two clusters of regions. The first cluster identified a distinct profile of correlation coefficients between 5-HT2A and D2 receptors, with the former in regions related to sensorimotor integration (supplementary motor area, superior parietal gyrus, and paracentral lobule) and the latter in most cortical regions. The second cluster identified another distinct profile of correlation coefficients between 5-HT2A receptors in the bilateral hippocampi and D2 receptors in most cortical regions. Conclusions The observation of two distinct clusters in the correlation matrix suggests regional interactions between 5-HT2A and D2 receptors in sensorimotor integration and hippocampal function. A bicluster analysis of the correlation matrix of these neuroreceptors may be beneficial in understanding molecular networks in the human brain.

Correction: Anatomical relationships between serotonin 5-HT2A and dopamine D2 receptors in living human brain

[This corrects the article DOI: 10.1371/journal.pone.0189318.].

Glutamatergic neurometabolite levels in major depressive disorder: a systematic review and meta-analysis of proton magnetic resonance spectroscopy studies

Alterations in glutamatergic neurotransmission are implicated in the pathophysiology of depression, and the glutamatergic system represents a treatment target for depression. To summarize the nature of glutamatergic alterations in patients with depression, we conducted a meta-analysis of proton magnetic resonance (1H-MRS) spectroscopy studies examining levels of glutamate. We used the search terms: depress* AND (MRS OR “magnetic resonance spectroscopy”). The search was performed with MEDLINE, Embase, and PsycINFO. The inclusion criteria were 1H-MRS studies comparing levels of glutamate + glutamine (Glx), glutamate, or glutamine between patients with depression and healthy controls. Standardized mean differences (SMD) were calculated to assess group differences in the levels of glutamatergic neurometabolites. Forty-nine studies met the eligibility criteria, which included 1180 patients and 1066 healthy controls. There were significant decreases in Glx within the medial frontal cortex (SMD = −0.38; 95% CI, −0.69 to −0.07) in patients with depression compared with controls. Subanalyses revealed that there was a significant decrease in Glx in the medial frontal cortex in medicated patients with depression (SMD = −0.50; 95% CI, −0.80 to −0.20), but not in unmedicated patients (SMD = −0.27; 95% CI, −0.76 to 0.21) compared with controls. Overall, decreased levels of glutamatergic metabolites in the medial frontal cortex are linked with the pathophysiology of depression. These findings are in line with the hypothesis that depression may be associated with abnormal glutamatergic neurotransmission.

FIRST-IN-HUMAN PET STUDY WITH 18 F-AM-PBB3 AND 18 F-PM-PBB3

to calculate white matter hyperintensity volume and total brain parenchyma volume by a blinded observer. Additionally, a subjective categorization of the distribution of white matter hyperintensity was assigned to each case by a blinded observer into one of three categories (central, peripheral, or mixed). Statistical analysis was performed to identify correlation between patterns of distribution, volume of hyperintensity, and presence /absence of disease and disease progression. Results:There was significant differences of the volume of hyperintensity with respect to distribution of disease within the normal (p1⁄4 0.002) and MCI (p1⁄4 0.046) subjects. There was a significant interaction (P 1⁄40.020) between the assigned pattern of white matter disease distribution and the subject’s disease burden. There was no association (p 1⁄4 0.221) between the disease status (normal controls, MCI with and without progression) and total volume of white matter hyperintensity, although this strengthened after adjusting for total parenchymal volume (p 1⁄4 0.131). Conclusions:The correlation between the pattern of brain white matter changes distribution and the disease status may help in determining which patients with MCI will be more likely to progress to dementia, therefore allowing directed therapy or better targeting of therapeutic trials. Additional characterization with a larger cohort including volumetric analysis of the white matter hyperintensity pattern and correlating with clinical diagnosis of metabolic syndrome could yield more specific resolution as to whether or not this can predict progression of MCI to dementia.