title: Sensitivity to reinforcer delay predicts ethanol's suppressant effects, but itself is unaffected by ethanol.
abstract: BACKGROUND
  Relative preference for smaller, sooner rewards over larger, later rewards ("delay discounting") is increased by acute ethanol. Additionally, drug-naïve levels of delay discounting can predict subsequent ethanol consumption. However, it is unknown whether these phenomena are driven by a difference in sensitivity to the reinforcer delay or a difference in sensitivity to the reinforcer magnitude, because typical delay discounting tasks manipulate both parameters simultaneously.
  
  
  METHODS
  To disambiguate these factors, two tasks were developed in which animals chose between levers with either different delay contingencies (adjusting delay task) or different magnitude contingencies (adjusting magnitude task). When task performance was stable, rats received ethanol (0, 0.6, and 0.9 g/kg, i.p.).
  
  
  RESULTS
  Ethanol did not affect sensitivity to delay or sensitivity to magnitude. However, responding was suppressed at the highest dose of ethanol (0.9 g/kg). Less suppression was found in animals exhibiting high levels of drug-naïve sensitivity to delay.
  
  
  CONCLUSIONS
  Thus, this study suggests that ethanol's effect on standard delay discounting tasks is not due to an alteration in sensitivity to delay or magnitude. Additionally, these data show that animals with high sensitivity to delay are resistant to the behaviorally suppressant effects of ethanol, which suggests that low tolerance for delayed rewards and low sensitivity to the behaviorally suppressant effects of ethanol may partly be driven by the same underlying mechanism.
authors.affiliation: Oregon Health & Science University, Portland, OR 97239-3098, USA. moschakt@ohsu.edu
authors.forename: Travis M
authors.initials: TM
authors.lastname: Moschak
authors.forename: Suzanne H
authors.initials: SH
authors.lastname: Mitchell
mesh_terms: D000818:Animals; D002492:Central Nervous System Depressants / Q000494:pharmacology*; D003216:Conditioning, Operant / Q000187:drug effects*; D003627:Data Interpretation, Statistical; D000431:Ethanol / Q000494:pharmacology*; D008297:Male; D051381:Rats; D020318:Rats, Long-Evans; D011930:Reaction Time / Q000502:physiology; D012044:Regression Analysis; D012054:Reinforcement, Psychology
chemical_list: D002492:Central Nervous System Depressants; D000431:Ethanol
keywords: Delay discounting; Ethanol; Impulsivity; Intertemporal choice; Low level of response to alcohol
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