title: Nucleus accumbens and delay discounting in rats: evidence from a new quantitative protocol for analysing inter-temporal choice.
abstract: BACKGROUND
  There is evidence that the core of the nucleus accumbens (AcbC) is involved in inter-temporal choice behaviour.
  
  
  OBJECTIVE
  A new behavioural protocol was used to examine the effect of destruction of the AcbC on delay discounting in inter-temporal choice schedules in rats.
  
  
  METHODS
  Rats with excitotoxic lesions of the AcbC or sham lesions made repeated choices on an adjusting-delay schedule between a smaller reinforcer (A) that was delivered immediately and a larger reinforcer (B) that was delivered after a delay which increased or decreased depending on the subject's choices. In two phases of the experiment, reinforcer sizes were selected which enabled theoretical parameters expressing delay discounting and sensitivity to reinforcer size to be estimated from the ratio of the indifference delays (i.e. the quasi-stable values of the adjusting delay seen after extended training) obtained in the two phases.
  
  
  RESULTS
  In both groups, indifference delays were shorter when the sizes of A and B were 14 and 25 μl than when they were 25 and 100 μl of a 0.6 M sucrose solution. Indifference delays were shorter in AcbC-lesioned than in sham-lesioned rats. Estimates of delay discounting rate based on the ratio of the indifference delays were lower in the AcbC-lesioned than in the sham-lesioned rats. The size sensitivity parameter did not differ between the groups. Adjusting delays in successive blocks of trials were analysed using Fourier transform. The period corresponding to the dominant frequency of the power spectrum and power within the dominant frequency band did not differ between the groups.
  
  
  CONCLUSIONS
  Destruction of the AcbC increased the rate of delay discounting.
authors: Psychopharmacology Section, Division of Psychiatry, University of Nottingham, Room B109, Medical School, Queen's Medical Centre, Nottingham, NG7 2UH, UK.
authors: L
authors: L
authors: Valencia-Torres
authors: C M
authors: CM
authors: Olarte-Sánchez
authors: S
authors: S
authors: da Costa Araújo
authors: S
authors: S
authors: Body
authors: C M
authors: CM
authors: Bradshaw
authors: E
authors: E
authors: Szabadi
mesh_terms: D000818:Animals; D002755:Choice Behavior / Q000502:physiology*; D003216:Conditioning, Operant / Q000187:drug effects / Q000502:physiology; D005260:Female; D007175:Impulsive Behavior / Q000503:physiopathology*; D008845:Microinjections; D008960:Models, Psychological; D009714:Nucleus Accumbens / Q000187:drug effects / Q000502:physiology*; D017378:Quinolinic Acid / Q000008:administration & dosage / Q000633:toxicity; D051381:Rats; D017208:Rats, Wistar; D012055:Reinforcement Schedule; D012054:Reinforcement, Psychology; D013997:Time Factors
chemical_list: D017378:Quinolinic Acid