title: Striatal dopamine synthesis capacity in twins discordant for schizophrenia.
abstract: BACKGROUND
  Elevated striatal dopamine synthesis capacity is thought to be fundamental to the pathophysiology of schizophrenia and has also been reported in people at risk of psychosis. It is therefore unclear if striatal hyperdopaminergia is a vulnerability marker for schizophrenia, or a state feature related to the psychosis itself. Relatives of patients with schizophrenia are themselves at increased risk of developing the condition. In this study we examined striatal dopamine synthesis capacity in both members of twin pairs discordant for schizophrenia.
  
  
  METHODS
  In vivo striatal dopamine synthesis capacity was examined using fluorine-18-l-dihydroxyphenylalanine (18F-DOPA) positron emission tomography (PET) scans in seven twin pairs discordant for schizophrenia and in a control sample of 10 healthy control twin pairs.
  
  
  RESULTS
  Striatal 18F-DOPA uptake was not elevated in the unaffected co-twins of patients with schizophrenia (p=0.65) or indeed in the twins with schizophrenia (p=0.89) compared to the control group. Levels of psychotic symptoms were low in the patients with schizophrenia who were in general stable [mean (s.d.) Positive and Negative Syndrome Scale (PANSS) total=56.8 (25.5)] whereas the unaffected co-twins were largely asymptomatic.
  
  
  CONCLUSIONS
  Striatal dopamine synthesis capacity is not elevated in symptom-free individuals at genetic risk of schizophrenia, or in well-treated stable patients with chronic schizophrenia. These findings suggest that striatal hyperdopaminergia is not a vulnerability marker for schizophrenia.
authors.affiliation: Psychiatric Imaging, MRC Clinical Sciences Centre, Hammersmith Hospital, Imperial College London, London, UK. p.shotbolt@imperial.ac.uk
authors.forename: P
authors.initials: P
authors.lastname: Shotbolt
authors.forename: P R
authors.initials: PR
authors.lastname: Stokes
authors.forename: S F
authors.initials: SF
authors.lastname: Owens
authors.forename: T
authors.initials: T
authors.lastname: Toulopoulou
authors.forename: M M
authors.initials: MM
authors.lastname: Picchioni
authors.forename: S K
authors.initials: SK
authors.lastname: Bose
authors.forename: R M
authors.initials: RM
authors.lastname: Murray
authors.forename: O D
authors.initials: OD
authors.lastname: Howes
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000378:metabolism; D016022:Case-Control Studies; D003342:Corpus Striatum / Q000378:metabolism*; D004200:Diseases in Twins / Q000378:metabolism*; D004298:Dopamine / Q000096:biosynthesis*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography; D012559:Schizophrenia / Q000378:metabolism*
chemical_list: D015415:Biomarkers; D004298:Dopamine