title: Effects of acute and sub-chronic nicotine on impulsive choice in rats in a probabilistic delay-discounting task.
abstract: BACKGROUND
  Cigarette smokers typically display impulsivity by preferring immediate rewards over larger, delayed rewards at shorter delays than do non-smokers. Suggesting causality, nicotine injections in rats increase the choice for an immediate reward over a larger, delayed reward.
  
  
  OBJECTIVE
  To examine the generality of this latter effect, the present study employed a delay-discounting task to determine if acute and sub-chronic nicotine will also increase impulsive choice when subjective reward value is manipulated by changes in the probability, rather than magnitude, of reward.
  
  
  METHODS
  Rats were presented with two levers, one of which delivered an immediate water reward on half of the trials, while the other lever delivered the same reward on every trial, but only after one of five increasing delays.
  
  
  RESULTS
  Acute injections of 1.2 mg/kg, but not 0.8 mg/kg, of nicotine increased the preference for the immediate (but less certain) reward lever at intermediate delays. Moreover, twice-daily injections of 0.8 mg/kg of nicotine for 6 days progressively increased the preference for the immediate reward. Latency to make the first response on each trial was not affected by nicotine.
  
  
  CONCLUSIONS
  The similar increases in impulsive choice produced by both acute and sub-chronic nicotine in delay-discounting paradigms whether subjective reward value is manipulated by changes in reward magnitude or probability suggests that nicotine may be increasing what is common to these paradigms, namely delay discounting. Whatever the mechanism, these data indicate that both acute and sub-chronic nicotine may help develop and maintain an addiction by increasing impulsivity.
authors: Department of Psychology and Program in Neuroscience, Bates College, Canham House, Room 103, 146 Wood St, Lewiston, ME 04240, USA. jkelsey@bates.edu
authors: John E
authors: JE
authors: Kelsey
authors: Anzela
authors: A
authors: Niraula
mesh_terms: D000818:Animals; D001522:Behavior, Animal; D002755:Choice Behavior / Q000187:drug effects*; D003216:Conditioning, Operant; D007175:Impulsive Behavior / Q000188:drug therapy* / Q000523:psychology; D008297:Male; D009538:Nicotine / Q000008:administration & dosage / Q000494:pharmacology*; D011336:Probability; D051381:Rats; D020318:Rats, Long-Evans; D011930:Reaction Time; D012055:Reinforcement Schedule; D012201:Reward; D013997:Time Factors
chemical_list: D009538:Nicotine