title: In vivo determination of muscarinic acetylcholine receptor availability in schizophrenia.
abstract: OBJECTIVE
  Postmortem studies have implicated the central muscarinic acetylcholine system in schizophrenia. However, central muscarinic receptor availability has not previously been studied in vivo. Using [I-123]iodoquinuclidinyl benzilate ([(123)I]IQNB) single photon emission computed tomography (SPECT), the authors sought to compare the muscarinic receptor availability in vivo in unmedicated patients with schizophrenia and normal subjects.
  
  
  METHODS
  Twelve medication-free patients with schizophrenia underwent an [(123)I]IQNB SPECT scan during approximate-equilibrium conditions. A group of 10 age- and gender-matched normal comparison subjects were given the same kind of scan under similar conditions. Regions of interest were analyzed in the cortex, basal ganglia, thalamus, and pons. Binding data were analyzed as nCi/ml tissue per mCi injected dose.
  
  
  RESULTS
  Muscarinic receptor availability was significantly less in patients with schizophrenia than in normal subjects in all regions of interest except the pons. Reductions ranged from -33% in the caudate to -20% in the occipital cortex. Positive symptoms of schizophrenia correlated negatively with muscarinic receptor availability in the striatum and the frontal cortex.
  
  
  CONCLUSIONS
  These results indicate a reduction in muscarinic acetylcholine receptor availability in vivo in unmedicated patients with schizophrenia, confirming results from postmortem studies and adding further evidence that the muscarinic system is involved in the pathophysiology of schizophrenia.
authors.affiliation: Clinical Brain Disorders Branch, NIMH, National Institutes of Health, 10 Center Dr., 4S-235, MSC 1379, Bethesda, MD 20892-1379, USA. weinberd@intra.nimh.nih.gov
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Raedler
authors.forename: Michael B
authors.initials: MB
authors.lastname: Knable
authors.forename: Douglas W
authors.initials: DW
authors.lastname: Jones
authors.forename: Richard A
authors.initials: RA
authors.lastname: Urbina
authors.forename: Julia G
authors.initials: JG
authors.lastname: Gorey
authors.forename: Kan S
authors.initials: KS
authors.lastname: Lee
authors.forename: Michael F
authors.initials: MF
authors.lastname: Egan
authors.forename: Richard
authors.initials: R
authors.lastname: Coppola
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Weinberger
mesh_terms: D000328:Adult; D001921:Brain / Q000000981:diagnostic imaging / Q000503:physiopathology; D001931:Brain Mapping; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes; D008297:Male; D008875:Middle Aged; D011813:Quinuclidinyl Benzilate; D011976:Receptors, Muscarinic / Q000502:physiology*; D012016:Reference Values; D012559:Schizophrenia / Q000000981:diagnostic imaging / Q000503:physiopathology*; D012565:Schizophrenic Psychology; D015899:Tomography, Emission-Computed, Single-Photon
chemical_list: D007457:Iodine Radioisotopes; D011976:Receptors, Muscarinic; C028484:quinuclidinyl benzilate receptor; D011813:Quinuclidinyl Benzilate