title: Increased synaptic dopamine in the putamen in restless legs syndrome.
abstract: OBJECTIVE
  Prior studies using positron emission tomography (PET) or single-photon emission computed tomography techniques have reported inconsistent findings regarding differences between patients with restless legs syndrome (RLS) and control patients in the striatal dopamine-2 receptor (D2R) binding potentials (BP). D2R-BP does reflect receptor-ligand interactions such as receptor affinity (K(d)) and density (β(max)) or neurotransmitter synaptic concentrations. Thus, differences in D2R-BP reflect changes in these primary factors. PET techniques are currently available to estimate D2R β(max) and K(d).
  
  
  METHODS
  Separate morning and evening PET scans were performed. The D2R-BP were measured in basal ganglia using [(11)C]raclopride.
  
  
  METHODS
  Academic medical center.
  
  
  METHODS
  Thirty-one patients with primary RLS and 36 age- and sex-matched control patients completed the study.
  
  
  RESULTS
  Patients with RLS had lower D2R-BP in putamen and caudate but not the ventral striatum. A subgroups analysis of those RLS patients who had not previously taken dopaminergic medications continued to show a significantly lower D2R-BP in the posterior putamen. D2R-BP did not differ between night and day for either group. D2R β(max) and K(d) did not differ significantly between patients with RLS and control patients but did show a strong and significant increase at night in the ventral striatum. Primary and secondary clinical measures of disease status failed to show any relation to D2R in any brain region.
  
  
  CONCLUSIONS
  Given the lack of any difference in either β(max) or K(d) and the prior studies supporting an increase in presynaptic dopaminergic activity, the current changes found in D2R-BP likely reflect an increase in synaptic dopamine.
authors.affiliation: Departments of Neurology, Johns Hopkins University, Baltimore, MD, USA. cearley@jhmi.edu
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Earley
authors.forename: Hiroto
authors.initials: H
authors.lastname: Kuwabara
authors.forename: Dean F
authors.initials: DF
authors.lastname: Wong
authors.forename: Charlene
authors.initials: C
authors.lastname: Gamaldo
authors.forename: Rachel E
authors.initials: RE
authors.lastname: Salas
authors.forename: James R
authors.initials: JR
authors.lastname: Brašić
authors.forename: Hayden T
authors.initials: HT
authors.lastname: Ravert
authors.forename: Robert F
authors.initials: RF
authors.lastname: Dannals
authors.forename: Richard P
authors.initials: RP
authors.lastname: Allen
mesh_terms: D001479:Basal Ganglia / Q000000981:diagnostic imaging / Q000378:metabolism; D002940:Circadian Rhythm; D004298:Dopamine / Q000378:metabolism*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography / Q000379:methods; D011699:Putamen / Q000378:metabolism*; D017448:Receptors, Dopamine D2 / Q000378:metabolism; D012148:Restless Legs Syndrome / Q000378:metabolism*; D013569:Synapses / Q000378:metabolism*
chemical_list: D017448:Receptors, Dopamine D2; D004298:Dopamine