title: Serotonin transporter residual availability during long-term antidepressant therapy does not differentiate responder and nonresponder unipolar patients.
abstract: BACKGROUND
  Serotonin transporters (SERT) are a major target for antidepressant medication, although there have been limited in vivo studies of SERT availability in patients being treated with antidepressants. It is not known whether SERT availability differs in treatment-responsive and -nonresponsive patients receiving long-term treatment. In this study, we used single photon emission computed tomography (SPECT) to compare SERT residual availability in unipolar responders and nonresponders during long-term antidepressant treatment. Dopamine transporter (DAT) availability was also assessed in the same patients to examine the relationship between the two transporter systems.
  
  
  METHODS
  Twenty-four medicated unipolar patients were recruited, of whom 11 were responders and 13 were nonresponders. All patients underwent SPECT with [123I] beta-carbomethoxy-3-beta-(4 iodophenyl)tropane. Brain SERT was measured in the brain stem and diencephalon, and DAT was measured in the striatum. Residual availability was calculated as a ratio of specific to nonspecific uptake, with the occipital region used as the nonspecific reference region.
  
  
  RESULTS
  There was no difference between responders and nonresponders in SERT availability. Dopamine transporter availability was similar in responders and nonresponders, and there was no association between SERT and DAT availability.
  
  
  CONCLUSIONS
  Serotonin transporter availability does not discriminate responders and nonresponders during long-term treatment with antidepressants.
authors.affiliation: Division of Community Based Sciences, Institute of Neurological Sciences, Southern General Hospital, Glasgow, United Kingdom. Jonathan.Cavanagh@clinmed.gla.ac.uk
authors.forename: Jonathan
authors.initials: J
authors.lastname: Cavanagh
authors.forename: James
authors.initials: J
authors.lastname: Patterson
authors.forename: Sally
authors.initials: S
authors.lastname: Pimlott
authors.forename: Deborah
authors.initials: D
authors.lastname: Dewar
authors.forename: Jos
authors.initials: J
authors.lastname: Eersels
authors.forename: Mary Frances
authors.initials: MF
authors.lastname: Dempsey
authors.forename: David
authors.initials: D
authors.lastname: Wyper
mesh_terms: D000328:Adult; D000375:Aging / Q000378:metabolism; D000928:Antidepressive Agents / Q000627:therapeutic use*; D000929:Antidepressive Agents, Tricyclic / Q000627:therapeutic use; D003511:Cyclohexanols / Q000627:therapeutic use; D003866:Depressive Disorder / Q000000981:diagnostic imaging / Q000188:drug therapy* / Q000235:genetics*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008803:Mianserin / Q000031:analogs & derivatives / Q000627:therapeutic use; D008875:Middle Aged; D000078785:Mirtazapine; D019275:Radiopharmaceuticals; D050486:Serotonin Plasma Membrane Transport Proteins / Q000378:metabolism*; D017367:Selective Serotonin Reuptake Inhibitors / Q000627:therapeutic use; D015899:Tomography, Emission-Computed, Single-Photon; D014326:Tropanes; D000069470:Venlafaxine Hydrochloride
chemical_list: D000928:Antidepressive Agents; D000929:Antidepressive Agents, Tricyclic; D003511:Cyclohexanols; D008803:Mianserin; D000078785:Mirtazapine; D019275:Radiopharmaceuticals; D050486:Serotonin Plasma Membrane Transport Proteins; D017367:Selective Serotonin Reuptake Inhibitors; D014326:Tropanes; D000069470:Venlafaxine Hydrochloride; C087552:2-carbomethoxy-8-(3-fluoropropyl)-3-(4-iodophenyl)tropane