title: A new criterion for acquisition of nicotine self-administration in rats.
abstract: BACKGROUND
  Acquisition of nicotine self-administration in rodents is relatively difficult to establish and measures of acquisition rate are sometimes confounded by manipulations used to facilitate the process. This study examined acquisition of nicotine self-administration without such manipulations and used mathematical modeling to define the criterion for acquisition.
  
  
  METHODS
  Rats were given 20 daily 2-h sessions occurring 6 days/week in chambers equipped with active and inactive levers. Each active lever press resulted in nicotine reinforcement (0-0.06 mg/kg, IV) and retraction of both levers for a 20-s time out, whereas inactive lever presses had no consequences. Acquisition was defined for individual rats by the higher likelihood of reinforcers obtained across sessions fitting a logistic over a constant function according to the corrected Akaike Information Criterion (AICc).
  
  
  RESULTS
  For rats that acquired self-administration, an AICc-based multi-model comparison demonstrated that the asymptote (highest number of reinforcers/session) and mid-point of the acquisition curve (h; the number of sessions necessary to reach half the asymptote) varied by nicotine dose, with both exhibiting a negative relationship (the higher the dose, the lower number of reinforcers and the lower h).
  
  
  CONCLUSIONS
  The modeling approach used in this study provides a way of defining acquisition of nicotine self-administration that takes advantage of all data from individual subjects and the procedure used is sensitive to dose differences in the absence of manipulations that influence acquisition (e.g., food restriction, prior food reinforcement, conditioned reinforcers).
authors.affiliation: Department of Psychology, Arizona State University, PO Box 871104, Tempe, AZ 85287-1104, United States.
authors.forename: Natalie A
authors.initials: NA
authors.lastname: Peartree
authors.forename: Federico
authors.initials: F
authors.lastname: Sanabria
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Thiel
authors.forename: Suzanne M
authors.initials: SM
authors.lastname: Weber
authors.forename: Timothy H C
authors.initials: TH
authors.lastname: Cheung
authors.forename: Janet L
authors.initials: JL
authors.lastname: Neisewander
mesh_terms: D000818:Animals; D003216:Conditioning, Operant / Q000187:drug effects*; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D016015:Logistic Models; D008297:Male; D009538:Nicotine / Q000008:administration & dosage*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012055:Reinforcement Schedule; D012054:Reinforcement, Psychology; D012646:Self Administration
chemical_list: D009538:Nicotine