Antipsychotic binding to the dopamine-3 receptor in humans: A PET study with [(11)C]-(+)-PHNO.

BACKGROUND: All currently available antipsychotic medications bind to both the dopamine-2 (D2) and dopamine-3 (D3) receptors in vitro. However, there is conflicting evidence from in vivo studies about whether or not antipsychotic medications bind to the D3 receptor (D3R). The purpose of this study was to determine whether acute doses of risperidone bind to the D3R in humans. METHODS: We performed PET scans on an mCT scanner with [(11)C]-(+)-PHNO injected as a bolus, before and after a 2mg oral dose of risperidone in five medication free subjects with schizophrenia. The subjects were scanned for 120min and underwent an MRI scan for region of interest delineation and coregistration. Cerebellum was used as a reference region. Simplified reference tissue modeling (SRTM) was used to calculate BPND. RESULTS: We observed binding to the D3R receptor by risperidone as evidenced by observable occupancy in regions in which the [(11)C]-(+)-PHNO signal is almost exclusively from the D3R (i.e., substantia nigra/ventral tegmental area). Using a regression model to estimate D2R:D3R selectivity, we observed a D2R:D3R selectivity of 2.1 for risperidone. CONCLUSION: Our preliminary results provide further support that acute doses of antipsychotic medications bind to the D3R and provide additional support for the further development of this receptor as a treatment target in schizophrenia.

Deficits in prefrontal cortical and extrastriatal dopamine release in schizophrenia: a positron emission tomographic functional magnetic resonance imaging study.

IMPORTANCE: Multiple lines of evidence suggest a deficit in dopamine release in the prefrontal cortex (PFC) in schizophrenia. Despite the prevalence of the concept of prefrontal cortical hypodopaminergia in schizophrenia, in vivo imaging of dopamine release in the PFC has not been possible until now, when the validity of using the positron emission tomographic D2/3 radiotracer carbon 11-labeled FLB457 in combination with the amphetamine paradigm was clearly established. OBJECTIVES: To (1) test amphetamine-induced dopamine release in the dorsolateral PFC (DLPFC) in drug-free or drug-naive patients with schizophrenia (SCZ) and healthy control (HC) individuals matched for age, sex, race/ethnicity, and familial socioeconomic status;(2) test blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging activation during a working memory task in the same participants; and (3) examine the relationship between positron emission tomographic and functional magnetic resonance imaging outcome measures. DESIGN, SETTING AND PARTICIPANTS: Positron emission tomographic imaging with carbon 11-labeled FLB457 before and following 0.5 mg/kg of amphetamine by mouth. Blood oxygenation level-dependent functional magnetic resonance imaging during the self-ordered working memory task. Twenty patients with schizophrenia recruited from the inpatient and outpatient research facilities at New York State Psychiatric Institute and 21 healthy control individuals participated, and data were acquired between June 16, 2011, and February 25, 2014. MAIN OUTCOMES AND MEASURE: The percentage change in binding potential (∆BPND) in the DLPFC following amphetamine, BOLD activation during the self-ordered working memory task compared with the control task, and the correlation between these 2 outcome measures. RESULTS: We observed significant differences in the effect of amphetamine on DLPFC BPND (mean [SD], ∆BPND in HC: -7.5% [11%]; SCZ: +1.8% [11%]; P = .01); a generalized blunting in dopamine release in SCZ involving most extrastriatal regions and the midbrain; and a significant association between ∆BPND and BOLD activation in the DLPFC in the overall sample including patients with SCZ and HC individuals. CONCLUSIONS AND RELEVANCE: To our knowledge, these results provide the first in vivo evidence for a deficit in the capacity for dopamine release in the DLPFC in SCZ and suggest a more widespread deficit extending to many cortical and extrastriatal regions including the midbrain. This contrasts with the well-replicated excess in dopamine release in the associative striatum in SCZ and suggests a differential regulation of striatal dopamine release in associative striatum vs extrastriatal regions. Furthermore, dopamine release in the DLPFC relates to working memory-related activation of this region, suggesting that blunted release may affect frontal cortical function.

Mental health screening and early intervention: clinical research study for under 5-year-old children in care in an inner London borough.

Typically the social-emotional development or mental health of under 5-year-old Children in Care (CiC) is not routinely assessed and there are few published data in the UK on the prevalence of difficulties for these children. Our hypothesis was that there could be a significant level of unidentified and unmet need within this group. A screening procedure was developed and piloted in a 12-month study assessing both child factors and the developing relationships between children and their caregivers. Previous screening studies have shown that recommendations for interventions are not reliably expedited. An intervention component was incorporated to address this and minimise delay in the children and their carers receiving support. Close inter-agency collaboration was integral to the establishment, implementation and high level of participation in the study. The screening proved acceptable to the majority of birth parents and caregivers, with 94% uptake of participants. In the year prior to screening only 10% of under-fives coming into care were identified as having difficulties in contrast to 67% of children in the screening cohort. The brief interventions offered were taken up in three-quarters of cases, leading to increased referrals on and access to mental health services for these children.

Serotonin 2A receptors in obsessive-compulsive disorder: a positron emission tomography study with [11C]MDL 100907.

BACKGROUND: Serotonergic abnormalities are hypothesized to contribute to obsessive-compulsive disorder (OCD). This study used positron emission tomography with the radioligand [11C]MDL 100907 to examine whether the distribution of serotonin 2A (5-HT(2A)) receptors is altered in OCD. METHODS: Nineteen OCD subjects, free of psychiatric medications and depression, and 19 matched healthy subjects underwent positron emission tomography scans following injection of [11C]MDL 100907. Total distribution volumes were derived by kinetic analysis using the arterial input function. Two measures of 5-HT(2A) availability were computed: the ratio at equilibrium of specifically bound radiotracer either to nondisplaceable radiotracer in tissue (BP(ND)) or to unmetabolized tracer in arterial plasma (BP(p)). Groups were compared using a region of interest (ROI) analysis and voxelwise analysis of spatially normalized parametric maps. ROIs included cortical (orbitofrontal, dorsolateral prefrontal, medial prefrontal, anterior cingulate, temporal, parietal, occipital, and insular cortex) and limbic (entorhinal cortex, parahippocampal gyrus, and medial temporal lobe) regions. RESULTS: No significant group differences were observed in [11C]MDL 100907 BP(ND) or BP(p) in the ROIs or in the voxelwise analysis of BP(ND) maps. There was a significant correlation in the orbitofrontal cortex between [11C]MDL 100907 binding and age of onset, with earlier age of onset associated with higher binding. CONCLUSIONS: Adults with OCD are not characterized as a group by major changes in 5-HT(2A) availability in cortical or limbic brain regions. Further research is warranted to examine potential differences in 5-HT(2A) availability between early- and late-onset OCD and to assess 5-HT(2A) function in relation to other neurotransmitter systems implicated in OCD.

Striatal and extrastriatal dopamine release measured with PET and [(18)F] fallypride.

The amphetamine challenge, in which positron emission tomography (PET) or single photon emission computed tomography radioligand binding following administration of amphetamine is compared to baseline values, has been successfully used in a number of brain imaging studies as an indicator of dopaminergic function, particularly in the striatum. [(18)F] fallypride is the first PET radioligand that allows measurement of the effects of amphetamine on D2/D3 ligand binding in striatum and extra-striatal brain regions in a single scanning session following amphetamine. We scanned 15 healthy volunteer subjects with [(18)F] fallypride at baseline and following amphetamine (0.3 mg/kg) using arterial plasma input-based modeling as well as reference region methods. We found that amphetamine effect was robustly detected in ventral striatum, globus pallidus, and posterior putamen, and with slightly higher variability in other striatal subregions. However, the observed effect sizes in striatum were less than those observed in previous studies in our laboratory using [(11)C] raclopride. Robust effect was also detected in limbic extra-striatal regions (hippocampus, amygdala) and substantia nigra, but the signal-to-noise ratio was too low to allow accurate measurement in cortical regions. We conclude that [(18)F] fallypride is a suitable ligand for measuring amphetamine effect in striatum and limbic regions, but it is not suitable for measuring the effect in cortical regions and may not provide the most powerful way to measure the effect in striatum.

Dose-occupancy study of striatal and extrastriatal dopamine D2 receptors by aripiprazole in schizophrenia with PET and [18F]fallypride.

Positron emission tomography (PET) and the high affinity D(2/3) radiotracer [(18)F]fallypride allow the assessment of D(2/3) receptor occupancy of antipsychotic drugs in striatal and extrastriatal brain regions. We measured regional occupancy attained across a range of clinical dosing by the partial D(2) agonist aripiprazole using these methods. Twenty-eight PET scans were acquired on the ECAT EXACT HR+ camera in 19 patients with schizophrenia or schizoaffective disorder. Daily aripiprazole doses ranged from 2 to 40 mg, with a minimum of 10 days on steady dose. Mean regional occupancies, a model-independent estimate of aripiprazole effect on pituitary binding, and PANSS ratings changes were evaluated. Occupancy levels were high across regions of interest, ranging from 71.6+/-5.5% at 2 mg/day to 96.8+/-5.3% at 40 mg/day. Occupancy levels were higher in extrastriatal than striatal regions. Pituitary measures of aripiprazole effect correlated with doses and were unrelated to prolactin levels, which remained within the normal range under medication. PANSS positive (but not negative) symptom improvement correlated with striatal but not extrastriatal occupancies. These data show, for the first time, D(2) occupancy by aripiprazole in treated patients with schizophrenia in extrastriatal as well as striatal regions, with high occupancy for all doses. We discuss possible explanations for higher extrastriatal than striatal occupancy. Correlations of ratings of clinical improvement with regional occupancy suggest that aripiprazole, as do other antipsychotics, benefits positive symptoms of schizophrenia most directly through its modulation of striatal rather than cortical or other extrastriatal dopamine activity.

A family of destabilized cyan fluorescent proteins as transcriptional reporters in S. cerevisiae.

The 'programmable' features of the N-end rule degradation pathway and a ubiquitin fusion strategy were exploited to create a family of destabilized cyan fluorescent proteins (CFP) to be used as transcriptional reporters. The N-degron CFP reporters characterized in this report have half-lives of approximately 75, 50 and 5 min, but further modification of the N-degron signal sequences could readily generate additional variants within this range. These destabilized CFP reporters have been engineered into convenient plasmid constructs with features to enable their expression from upstream activating sequences of choice and to facilitate their targeted integration to the URA3-TIM9 intergenic region of chromosome V. The advantages and limitations of these reporters as temporal indicators of gene expression in living cells are illustrated by their application as reporters of galactose- and pheromone-induced transcription. The plasmid design we describe and the range of different stabilities that are theoretically feasible with this strategy make the N-degron CFP reporters easily adapted to a variety of applications.

Biodistribution and radiation dosimetry of the dopamine D2 ligand 11C-raclopride determined from human whole-body PET.

UNLABELLED: Whole-body radiation dosimetry of 11C-raclopride was performed in healthy human volunteers. METHODS: Subjects (n = 6) were scanned with PET. Subjects received single-bolus injections of 11C-raclopride (S-(-)-3,5-dichloro-N-[(1-ethyl-2-pyrrolidinyl)]methyl-2-hydroxy-6-methoxybenzamide) (533 +/- 104 MBq) and were scanned for approximately 110 min with a 2-dimensional whole-body protocol. Regions of interest were placed over all visually identifiable organs and time-activity curves were generated. Residence times were computed as the area under the curve of the time-activity curves, normalized to injected activities and standard values of organ volumes. Absorbed doses were computed according to the MIRD schema with MIRDOSE3.1 software. RESULTS: Organs with the highest radiation burden were gallbladder wall, small intestine, liver, and urinary bladder wall. CONCLUSION: On the basis of the estimated absorbed dose, the maximum allowable single study dose under U.S. federal regulations for studies performed under Radiation Drug Research Committee is 1.58 GBq (42.8 mCi). This is still considerably higher than the doses of 11C-raclopride commonly used in research PET (370-555 MBq).

Unique occupational hazards of Alaska: animal-related injuries.

OBJECTIVE: During 1992-2000, an average of 40 fatal occupational injuries and 12,400 nonfatal occupational injuries and illnesses related to animals were recorded each year in the United States, most involving domestic farm animals. Although Alaska has a relatively small farming industry, it supports several industries that require workers to regularly be in contact with animals. This study examines the pattern and characteristics of animal-related occupational injuries in Alaska. METHODS: Two data sources were accessed: the Alaska Trauma Registry for nonfatal injuries requiring hospitalization and the Alaska Occupational Injury Surveillance System for fatal injuries. The case definition included events in which the source of the injury was an animal or animal product (Occupational Injury and Illness Classification Manual source code 51). RESULTS: In Alaska during 1991-2000, there were 43 animal-related occupational injuries requiring hospitalization and 25 animal-related fatalities. There were only 2 fatal events: 1 bird-strike aircraft accident killing 24 military personnel and 1 bear attack. The majority of the nonfatal injury events were related to marine wildlife (n = 20), with the rest related to either domesticated (n = 11) or nondomesticated (n = 12) mammals. Of events reporting a hospital charge (23 of 43), the average cost was over dollar 9700 per person. CONCLUSIONS: The catastrophic aircraft crash increased bird-control efforts near airports around the state. The nonfatal animal-related injuries have received less notice, although they result in thousands of dollars in hospital costs and lost workdays. Fishing-industry workers in particular should be made aware of potential injuries and educated on how to treat them when away from definitive medical care.

Persistent activation by constitutive Ste7 promotes Kss1-mediated invasive growth but fails to support Fus3-dependent mating in yeast.

Mitogen-activated protein kinase kinase kinase-Ste11 (MAPKKK-Ste11), MAPKK-Ste7, and MAPK-Kss1 mediate pheromone-induced mating differentiation and nutrient-responsive invasive growth in Saccharomyces cerevisiae. The mating pathway also requires the scaffold-Ste5 and the additional MAPK-Fus3. One contribution to specificity in this system is thought to come from stimulus-dependent recruitment of the MAPK cascade to upstream activators that are unique to one or the other pathway. To test this premise, we asked if stimulus-independent signaling by constitutive Ste7 would lead to a loss of biological specificity. Instead, we found that constitutive Ste7 promotes invasion without supporting mating responses. This specificity occurs because constitutive Ste7 activates Kss1, but not Fus3, in vivo and promotes filamentation gene expression while suppressing mating gene expression. Differences in the ability of constitutive Ste7 variants to bind the MAPKs and Ste5 account for the selective activation of Kss1. These findings support the model that Fus3 activation in vivo requires binding to both Ste7 and the scaffold-Ste5 but that Kss1 activation is independent of Ste5. This scaffold-independent activation of Kss1 by constitutive Ste7 and the existence of mechanisms for pathway-specific promoter discrimination impose a unique developmental fate independently of any distinguishing external stimuli.

"Death was a blessing"--should it ever be pharmaceutically hastened? British pharmacists' views.

OBJECTIVES: To investigate the views and experiences of British pharmacists in physician-assisted suicide (PAS) and voluntary active euthanasia (VAE) and to examine whether differences in views were associated with personal characteristics. METHOD: A postal questionnaire was mailed to a random sample of 500 registered pharmacists, with addresses in England or Wales, stratified according to sex and community/hospital working environments. MAIN OUTCOME MEASURE: Pharmacists' reports of their views and experiences of PAS and VAE. RESULTS: Completed questionnaires were received from 295 respondents (response rate: 59%). The majority of respondents (83%) reported that at times, a person had the right to choose their own manner of death; 61% and 53% thought that there should be changes in the Law to legalise VAE and PAS, respectively. If it were legal to do so, 63% stated that they would be willing to dispense medication for VAE and 64% for PAS. However, only 45% agreed that the pharmacist should have a role in advising the prescriber on the choice and dose of drugs used. Sex, age, and years registered as a pharmacist were not found to be significantly associated with views on the practices of PAS and VAE. However, pharmacists who reported having a religion were significantly less likely to favour such practices. On comparing the views of community and hospital pharmacists, community pharmacists were significantly less likely than expected to want to be informed about the intended purpose of lethal drugs. CONCLUSION: In this survey, while over half of British pharmacists did not disagree in principle to the legalisation of VAE and/or PAS, they were less supportive of direct involvement in such procedures. Religion was a discriminatory factor associated with negative views of VAE and PAS. The significant minority of pharmacists not wanting to know the purpose of drugs they suspected might be for PAS or VAE is not in accordance with professional accountability, reflecting the complex and sometimes conflicting legal and moral aspects of such practices when deciding upon a course of action.

Inactivation of adenosine A2A receptors selectively attenuates amphetamine-induced behavioral sensitization.

Repeated treatment with the psychostimulant amphetamine produces behavioral sensitization that may represent the neural adaptations underlying some features of psychosis and addiction in humans. In the present study we investigated the role of adenosine A(2A) receptors in psychostimulant-induced locomotor sensitization using an A(2A) receptor knockout (A(2A) KO) model. Daily treatment with amphetamine for 1 week resulted in an enhanced motor response on day 8 (by two-fold compared to that on day 1), and remained enhanced at day 24 upon rechallenge with amphetamine. By contrast, locomotor sensitization to daily amphetamine did not develop in A(2A) KO mice on day 8 or 24, and this absence was not the result of a nonspecific threshold effect. The absence of behavioral sensitization was selective for amphetamine since daily treatment with the D(1) agonist SKF81297 (2.5 mg/kg) or the D(2) agonist quinpirole (1.0 mg/kg) produced similar behavioral sensitization in both WT and A(2A) KO mice. Furthermore, coinjection of SKF81297 and quinpirole also resulted in indistinguishable locomotor sensitization in A(2A) KO and WT mice, suggesting normal D(1) and D(2) receptor responsiveness. Finally, at the cellular level A(2A) receptor inactivation abolished the increase in striatal dynorphin mRNA induced by repeated amphetamine administration. The selective absence of amphetamine-induced behavioral sensitization in A(2A) KO mice suggests a critical role of the A(2A) receptor in the development of psychostimulant-induced behavioral sensitization, and supports the pharmacological potential of A(2A) adenosinergic agents to modulate adaptive responses to repeated psychostimulant exposure.

Efficacy of sertraline in the long-term treatment of obsessive-compulsive disorder.

OBJECTIVE: Obsessive-compulsive disorder (OCD) typically begins early in life and has a chronic course. Despite the need for long-term treatment, the authors found no placebo-controlled studies that have examined the relapse-prevention efficacy of maintenance therapy. METHOD: Patients who met criteria for response after 16 and 52 weeks of a single-blind trial of sertraline were randomly assigned to a 28-week double-blind trial of 50-200 mg/day of sertraline or placebo. Primary outcomes after the double-blind trial were full relapse, dropout due to relapse or insufficient response, or acute exacerbation of OCD symptoms. RESULTS: Of 649 patients at baseline, 232 completed 52 weeks of the single-blind trial and met response criteria. Among the 223 patients in the double-blind phase of the study, sertraline had significantly greater efficacy than placebo on two of three primary outcomes: dropout due to relapse or insufficient clinical response (9% versus 24%, respectively) and acute exacerbation of symptoms (12% versus 35%). Sertraline resulted in improvement in quality of life during the initial 52-week trial and continued improvement, significantly superior to placebo, during the subsequent 28-week double-blind trial. Long-term treatment with sertraline was well tolerated. Over the entire study period, less than 20% of the patients stopped treatment because of adverse events. CONCLUSIONS: Sertraline demonstrated sustained efficacy among patients responding to treatment and was generally well tolerated during the 80-week study. During the study's last 28 weeks, sertraline demonstrated greater efficacy than placebo in preventing dropout due to relapse or insufficient clinical response and acute exacerbation of OCD symptoms.