title: SERT-to-DAT ratios in early Parkinson's disease do not correlate with the development of dyskinesias.
abstract: BACKGROUND
  Although the treatment of Parkinson's disease (PD) is very effective, in the course of the disease, 40% to 60% of patients develop dyskinesias. The pathophysiology of dyskinesias is still unclear. Results of preclinical research suggest that uptake and uncontrolled release of dopamine by serotonergic neurons is an important factor. Based on this model, we hypothesized that dyskinesias will develop predominantly in PD patients with a relatively preserved serotonergic system.
  
  
  METHODS
  Between 1995 and 1998, 50 patients with early-stage untreated PD, diagnosed according to clinical criteria, and reduced striatal [123I]β-carboxymethyoxy-3-beta-(4-iodophenyl) tropane (CIT) single-photon emission computed tomography (SPECT) binding were recruited. To test our hypothesis, we retrospectively assessed baseline [123I]β-CIT SPECT scans for striatal dopamine transporter (DAT) and midbrain serotonin transporter (SERT) availability as well as the SERT-to-DAT ratios. We compared these data between patients that developed dyskinesias and patients that did not develop dyskinesias during a mean follow-up of 14.2 years.
  
  
  RESULTS
  Approximately half of the PD patients developed dyskinesias. No differences in baseline [123I]β-CIT DAT availability, SERT availability, or SERT-to-DAT ratios were found between the dyskinetic and non-dyskinetic group. The development of dyskinesias was most strongly associated with the age of onset (P = 0.002).
  
  
  CONCLUSIONS
  SERT-to-DAT ratios in early-stage untreated PD do not correlate with the future development of dyskinesias. However, our study does not exclude the possibility that SERT-to-DAT ratios increase with disease progression in patients that develop dyskinesias because of a slower rate of degeneration of the serotonergic system.
authors.affiliation: Department of Neurology, H2-225, Academic Medical Center, University of Amsterdam, PO Box 22660, Amsterdam 1100 DD, The Netherlands. s.r.suwijn@amc.uva.nl.
authors.forename: Sven R
authors.initials: SR
authors.lastname: Suwijn
authors.forename: Henk W
authors.initials: HW
authors.lastname: Berendse
authors.forename: Constant Vm
authors.initials: CV
authors.lastname: Verschuur
authors.forename: Ania
authors.initials: A
authors.lastname: Winogrodzka
authors.forename: Rob Ma
authors.initials: RM
authors.lastname: de Bie
authors.forename: Jan
authors.initials: J
authors.lastname: Booij