title: Impulsivity and drugs of abuse: a juice-reinforced operant procedure for determining within-session delay discounting functions in rhesus monkeys.
abstract: BACKGROUND
  Impulsivity is a behavioral trait that is thought to contribute to a variety of disorders, including drug abuse. Efficient, sensitive procedures are needed for studying drug effects on impulsivity (e.g., delay discounting) in nonhumans.
  
  
  METHODS
  Three monkeys responded under an operant choice procedure whereby responses on one lever resulted in immediate delivery of 0.15 ml of juice [Hawaiian Punch®] and responses on another lever resulted in delivery of 0.75 ml of juice, either immediately or after a delay (3.75-40 s). The delay to the larger reinforcer increased within-session across discrete blocks allowing for generation of delay-discounting functions within sessions.
  
  
  RESULTS
  Without delay, monkeys chose the larger reinforcer nearly exclusively. With increasing delay, monkeys progressively switched their choice from the larger to the smaller reinforcer in a delay-dependent manner. In 2 monkeys, acute administration of morphine (0.1 and 0.32 mg/kg) or ketamine (0.1 and 0.32 mg/kg) but not diazepam (0.1-1.0 mg/kg) dose-dependently shifted the delay-discounting functions to the left, indicating increased discounting. In one monkey, daily morphine treatment (0.32 mg/kg/day, 3-hour pretreatment) produced a rapid, sustained leftward shift in the delay-discounting function; the curve returned to the pre-drug position 6 days after discontinuation of treatment.
  
  
  CONCLUSIONS
  This delay discounting procedure is sensitive to both behavioral and pharmacological manipulations and appears to be particularly sensitive to chronic drug treatment and drug withdrawal. Given the importance of drug dependence and withdrawal in the initiation, maintenance of, and relapse to drug taking, this procedure should be useful to study one aspect of this process.
authors.affiliation: Department of Pharmacology, The University of Texas Health Science Center at San Antonio, San Antonio, TX, USA.
authors.forename: David R
authors.initials: DR
authors.lastname: Maguire
authors.forename: Jun-Xu
authors.initials: JX
authors.lastname: Li
authors.forename: Charles P
authors.initials: CP
authors.lastname: France
mesh_terms: D000818:Animals; D001628:Beverages; D002755:Choice Behavior / Q000187:drug effects*; D003216:Conditioning, Operant / Q000187:drug effects*; D003975:Diazepam / Q000008:administration & dosage / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005260:Female; D007175:Impulsive Behavior; D007649:Ketamine / Q000008:administration & dosage / Q000494:pharmacology; D008253:Macaca mulatta; D008297:Male; D009020:Morphine / Q000008:administration & dosage / Q000494:pharmacology; D012055:Reinforcement Schedule; D012646:Self Administration; D013997:Time Factors
chemical_list: D007649:Ketamine; D009020:Morphine; D003975:Diazepam