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Ballanger B.,Vivian koff Pet Center | Strafella A.P.,Vivian koff Pet Center | Strafella A.P.,Movement Disorders Center | Strafella A.P.,University of Toronto | And 5 more authors.
Archives of Neurology | Year: 2010

Background: Complex visual hallucinations (VHs) occur in several pathologic conditions; however, the neural mechanisms underlying these symptoms remain unclear. Although dopamine may have a role, indirect evidence indicates that serotonin may also contribute to the pathogenesis of complex VHs, probably via involvement of the serotonin 2 receptor. Objective: To examine for the first time in vivo changes in serotonin 2A receptor neurotransmission among patients having Parkinson disease (PD) with VHs. Design: Case-control study. Setting: Academic research. Patients: Seven patients having PD with VHs and 7 age-matched patients having PD without VHs were recruited. Main Outcome Measures: We used the selective serotonin 2A receptor ligand setoperone F 18 during positron emission tomography among nondemented patients having PD with VHs. Results: Patients having PD with VHs demonstrate increased serotonin 2A receptor binding in the ventral visual pathway (including the bilateral inferooccipital gyrus, right fusiform gyrus, and inferotemporal cortex) as well as the bilateral dorsolateral prefrontal cortex, medial orbitofrontal cortex, and insula. Conclusions: This pilot study provides the first in vivo evidence suggesting a role for serotonin 2A receptors in mediating VHs via the ventral visual pathway in PD. Treatment studies should be performed using selective serotonin 2A receptor antagonists, which have important implications for the clinical management of VHs and psychosis in PD. ©2010 American Medical Association. All rights reserved.

Mizrahi R.,Vivian koff Pet Center | Rusjan P.M.,Vivian koff Pet Center | Vitcu I.,Vivian koff Pet Center | Ng A.,Vivian koff Pet Center | And 3 more authors.
Molecular Imaging and Biology | Year: 2013

Purpose: [18F]-FEPPA is a translocator protein (18 kDa, TSPO) positron emission tomography (PET) radiotracer. Radiation dosimetry was estimated from the whole body biodistribution, taking into consideration TSPO rs6971 (Ala147Thr) polymorphism. Procedures: [18F]-FEPPA whole body PET scans were acquired for six healthy subjects. Time-activity curves were generated from regions of interest of nine organs, from which normalized accumulated activities were calculated and thus internal dose, using OLINDA/EXM 1.1. Genotyping of rs6971, associated with high- and low-affinity [ 18F]-FEPPA binding (high-affinity binder (HAB) and low-affinity binder (LAB)), was performed. Results: Five subjects exhibited the C/C (HAB) allele, and the other carried the minor allele T/T (LAB). The LAB whole body biodistribution showed highest radioactivity accumulation in bladder, whereas in HABs, the spleen received the highest dose. The effective dose of the single LAB (16.3 μSv/MBq) was 23 % less than the mean of the HABs (21.0 ± 2.9 μSv/MBq). When including all subjects, the effective dose was 20.2 ± 3.0 μSv/MBq. Conclusions: [18F]-FEPPA radiation dose is consistent with other 18F-labeled radioligands and the Ala147Thr genotype agreed with [18F]-FEPPA distribution. © 2012 World Molecular Imaging Society.

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