title: Monetary discounting and ventral striatal dopamine receptor availability in nontreatment-seeking alcoholics and social drinkers.
abstract: BACKGROUND
  Dopamine (DA) in the ventral striatum (VST) has long been implicated in addiction pathologies, yet its role in temporal decision-making is not well-understood.
  
  
  OBJECTIVE
  To determine if VST DA D2 receptor availability corresponds with greater impulsive choice in both nontreatment-seeking alcoholics (NTS) and social drinkers (SD).
  
  
  METHODS
  NTS subjects (n = 10) and SD (n = 13) received PET scans at baseline with the D2/D3 radioligand [(11)C]raclopride (RAC). Outside the scanner, subjects performed a delay discounting procedure with monetary rewards. RAC binding potential (BPND) was estimated voxelwise, and correlations were performed to test for relationships between VST BPND and delay discounting performance. Self-reported impulsivity was also tested for correlations with BPND.
  
  
  RESULTS
  Across all subjects, greater impulsive choice for $20 correlated with lower BPND in the right VST. NTS showed greater impulsive choice than SD and were more impulsive by self-report. Across all subjects, the capacity of larger rewards to reduce impulsive choice (the magnitude effect) correlated negatively (p = 0.028) with problematic alcohol use (AUDIT) scores. Self-reported impulsivity did not correlate with BPND in VST.
  
  
  CONCLUSIONS
  Preference for immediate reinforcement may reflect greater endogenous striatal DA or lower D2 number, or both. Alcoholic status did not mediate significant effects on VST BPND, suggesting minimal effects from alcohol exposure. The apparent lack of BPND correlation with self-reported impulsivity highlights the need for objective behavioral assays in the study of the neurochemical substrates of behavior. Finally, our results suggest that the magnitude effect may be more sensitive to alcohol-induced problems than single discounting measures.
authors.affiliation: Indiana University Center for Neuroimaging, Indianapolis, IN, USA.
authors.forename: Brandon G
authors.initials: BG
authors.lastname: Oberlin
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Albrecht
authors.forename: Christine M
authors.initials: CM
authors.lastname: Herring
authors.forename: James W
authors.initials: JW
authors.lastname: Walters
authors.forename: Karen L
authors.initials: KL
authors.lastname: Hile
authors.forename: David A
authors.initials: DA
authors.lastname: Kareken
authors.forename: Karmen K
authors.initials: KK
authors.lastname: Yoder
mesh_terms: D000328:Adult; D000428:Alcohol Drinking / Q000378:metabolism* / Q000523:psychology*; D057229:Alcoholics / Q000523:psychology*; D003342:Corpus Striatum / Q000000981:diagnostic imaging / Q000187:drug effects* / Q000378:metabolism*; D004298:Dopamine / Q000378:metabolism; D018492:Dopamine Antagonists / Q000494:pharmacology; D004522:Educational Status; D005260:Female; D006801:Humans; D007175:Impulsive Behavior; D008297:Male; D008875:Middle Aged; D020891:Raclopride / Q000494:pharmacology; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals; D011954:Receptors, Dopamine / Q000187:drug effects / Q000378:metabolism*; D017448:Receptors, Dopamine D2 / Q000187:drug effects; D012054:Reinforcement, Psychology; D012201:Reward; D055815:Young Adult
chemical_list: D018492:Dopamine Antagonists; D019275:Radiopharmaceuticals; D011954:Receptors, Dopamine; D017448:Receptors, Dopamine D2; D020891:Raclopride; D004298:Dopamine