title: Examining endogenous dopamine in treated schizophrenia using [¹¹C]-(+)-PHNO positron emission tomography: A pilot study.
abstract: BACKGROUND
  Using positron emission tomography (PET) it is possible to estimate endogenous dopamine (DA) occupying D2/3 receptors (D2/3R) in the living human brain. Persons with schizophrenia (SZ) (previously medicated and naïve) have increased endogenous DA occupying D2/3R in the caudate. It is unknown whether currently medicated patients demonstrate increased DA levels at D2/3R. Moreover, DA levels have not been estimated in SZ using agonist radiotracers, which may offer a more sensitive quantification over antagonists.
  
  
  METHODS
  Using the agonist radiotracer [(11)C]-(+)-PHNO, DA levels were estimated at D2/3R (ΔBP(ND)) in three patients with SZ (male, mean age=30±16). Patients were currently being treated long-term with Olanzapine (147±88 nmol/L). Results were compared to ten healthy controls (HCs).
  
  
  RESULTS
  Medicated persons with SZ had greater ΔBP(ND) in the left caudate (U=2, Z=-2.20, p=.03) and right putamen (U=2, Z=-2.20, p=.03). No differences were observed in the ventral striatum or globus pallidus.
  
  
  CONCLUSIONS
  It is possible to estimate endogenous DA at D2/3R in SZ patients currently taking antipsychotics. Despite medication, patients continue to have increased endogenous DA at D2/3R. This lends more biological support to the clinical observation that relapses in symptoms can occur in the face of complete antipsychotic discontinuation. Future studies with larger samples are warranted.
authors: Research Imaging Centre, Centre for Addiction and Mental Health, 250 College Street, Toronto, Ontario M5T 1R8, Canada; Institute of Medical Science, University of Toronto, 2374 Medical Sciences Building, 1 King's College Circle, Toronto, Ontario M5S 1A8, Canada.
authors: Fernando
authors: F
authors: Caravaggio
authors: Research Imaging Centre, Centre for Addiction and Mental Health, 250 College Street, Toronto, Ontario M5T 1R8, Canada.
authors: Carol
authors: C
authors: Borlido
authors: Research Imaging Centre, Centre for Addiction and Mental Health, 250 College Street, Toronto, Ontario M5T 1R8, Canada; Institute of Medical Science, University of Toronto, 2374 Medical Sciences Building, 1 King's College Circle, Toronto, Ontario M5S 1A8, Canada; Department of Psychiatry, University of Toronto, 250 College Street, Toronto, Ontario M5T 1R8, Canada.
authors: Alan
authors: A
authors: Wilson
authors: Research Imaging Centre, Centre for Addiction and Mental Health, 250 College Street, Toronto, Ontario M5T 1R8, Canada; Institute of Medical Science, University of Toronto, 2374 Medical Sciences Building, 1 King's College Circle, Toronto, Ontario M5S 1A8, Canada; Department of Psychiatry, University of Toronto, 250 College Street, Toronto, Ontario M5T 1R8, Canada. Electronic address: ariel.graff@camh.ca.
authors: Ariel
authors: A
authors: Graff-Guerrero
mesh_terms: D000328:Adult; D002250:Carbon Radioisotopes / Q000378:metabolism*; D004298:Dopamine / Q000378:metabolism*; D018491:Dopamine Agonists / Q000378:metabolism*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010865:Pilot Projects; D049268:Positron-Emission Tomography / Q000379:methods; D012559:Schizophrenia / Q000000981:diagnostic imaging* / Q000378:metabolism*; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D002250:Carbon Radioisotopes; D018491:Dopamine Agonists; D004298:Dopamine
keywords: D(2/3)R; Dopamine; PET; Schizophrenia