title: A modified adjusting delay task to assess impulsive choice between isocaloric reinforcers in non-deprived male rats: effects of 5-HT₂A/C and 5-HT₁A receptor agonists.
abstract: BACKGROUND
  Existing animal models of impulsivity frequently use food restriction to increase subjects' motivation. In addition, behavioral tasks that assess impulsive choice typically involve the use of reinforcers with dissimilar caloric content. These factors represent energy-homeostasis limitations, which may confound the interpretation of results and limit the applicability of these models.
  
  
  OBJECTIVE
  This study was aimed at validating face and convergent validities of a modified adjusting delay task, which assesses impulsive choice between isocaloric reinforcers in ad libitum fed rats.
  
  
  METHODS
  Male Wistar rats (n = 18) were used to assess the preferredness and reinforcing efficacy of a "supersaccharin" solution (1.5% glucose/0.4% saccharin) over a 1.5% glucose solution. A separate group of rats (n = 24) was trained in a modified adjusting delay task, which involved repeated choice between the glucose solution delivered immediately and the supersaccharin solution delivered after a variable delay. To pharmacologically validate the task, the effects of the 5-HT(2A/C) receptor agonist (±)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane [(±)-DOI] and the 5-HT(1A) receptor agonist (±)-8-hydroxy-2-(dipropylamino)tetralin hydrobromide [(±)-8-OH-DPAT] on impulsive choice were then evaluated.
  
  
  RESULTS
  Supersaccharin was highly reinforcing and uniformly preferred over the glucose solution by all subjects. Rats quickly learned the task, and impulsivity was a very stable and consistent trait. DOI and 8-OH-DPAT significantly and dose dependently increased impulsive choice in this modified adjusting delay task.
  
  
  CONCLUSIONS
  We validated a rodent task of impulsive choice, which eliminates typical energy-homeostasis limitations and, therefore, opens new avenues in the study of impulsivity in preclinical feeding and obesity research.
authors: Laboratory of Addictive Disorders, Department of Pharmacology and Experimental Therapeutics, Boston University School of Medicine, 72 E Concord St, R-618, Boston, MA 02118, USA. blasio@bu.edu
authors: Angelo
authors: A
authors: Blasio
authors: Aditi R
authors: AR
authors: Narayan
authors: Barbara J
authors: BJ
authors: Kaminski
authors: Luca
authors: L
authors: Steardo
authors: Valentina
authors: V
authors: Sabino
authors: Pietro
authors: P
authors: Cottone
mesh_terms: D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000494:pharmacology / Q000627:therapeutic use; D000662:Amphetamines / Q000494:pharmacology / Q000627:therapeutic use; D000818:Animals; D002755:Choice Behavior / Q000187:drug effects*; D003216:Conditioning, Operant / Q000187:drug effects*; D005947:Glucose / Q000494:pharmacology; D007175:Impulsive Behavior / Q000188:drug therapy*; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D012201:Reward; D012439:Saccharin / Q000494:pharmacology; D058825:Serotonin 5-HT1 Receptor Agonists / Q000494:pharmacology / Q000627:therapeutic use*; D058826:Serotonin 5-HT2 Receptor Agonists / Q000494:pharmacology / Q000627:therapeutic use*; D013997:Time Factors
chemical_list: D000662:Amphetamines; D058825:Serotonin 5-HT1 Receptor Agonists; D058826:Serotonin 5-HT2 Receptor Agonists; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D012439:Saccharin; D005947:Glucose; C015952:4-iodo-2,5-dimethoxyphenylisopropylamine