title: Comparison of self-administration behavior and responsiveness to drug-paired cues in rats running an alley for intravenous heroin and cocaine.
abstract: BACKGROUND
  Evidence suggests that responsiveness to a drug-paired cue is predicted by the reinforcing magnitude of the drug during prior self-administration. It remains unclear, however, if this principle holds true when comparisons are made across drug reinforcers.
  
  
  OBJECTIVE
  The current study was therefore devised to test the hypothesis that differences in the animals' responsiveness to a cocaine- or heroin-paired cue presented during extinction would reflect differences in the patterns of prior cocaine and heroin runway self-administration.
  
  
  METHODS
  Rats ran a straight alley for single intravenous injections of either heroin (0.1 mg/kg/inj) or cocaine (1.0 mg/kg/inj) each paired with a distinct olfactory cue. Animals experienced 15 trials with each drug reinforcer in a counterbalanced manner. Start latencies, run times, and retreat behaviors (a form of approach-avoidance conflict) provided behavioral indices of the subjects' motivation to seek the reinforcer on each trial. Responsiveness to each drug-paired cue was assessed after 7, 14, or 21 days of non-reinforced extinction trials. Other animals underwent conditioned place preference (CPP) testing to ensure that the two drug reinforcers were capable of producing drug-cue associations.
  
  
  RESULTS
  While both drugs produced comparable CPPs, heroin served as a stronger incentive stimulus in the runway as evidenced by faster start and run times and fewer retreats. In contrast, cocaine- but not heroin-paired cues produced increases in drug-seeking behavior during subsequent extinction trials.
  
  
  CONCLUSIONS
  The subjects' responsiveness to drug-paired cues during extinction was not predicted by differences in the motivation to seek heroin versus cocaine during prior drug self-administration.
authors.affiliation: Department of Psychology, University of California, Santa Barbara, CA 93106-9660, USA.
authors.forename: Zu-In
authors.initials: ZI
authors.lastname: Su
authors.forename: Jennifer
authors.initials: J
authors.lastname: Wenzel
authors.forename: Rebeccah
authors.initials: R
authors.lastname: Baird
authors.forename: Aaron
authors.initials: A
authors.lastname: Ettenberg
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D003042:Cocaine / Q000008:administration & dosage*; D003216:Conditioning, Operant / Q000187:drug effects*; D003463:Cues; D058999:Drug-Seeking Behavior / Q000187:drug effects*; D003932:Heroin / Q000008:administration & dosage*; D008124:Locomotion / Q000187:drug effects; D008297:Male; D009294:Narcotics / Q000008:administration & dosage*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011930:Reaction Time / Q000187:drug effects; D012054:Reinforcement, Psychology; D012646:Self Administration / Q000379:methods / Q000523:psychology; D013997:Time Factors
chemical_list: D009294:Narcotics; D003932:Heroin; D003042:Cocaine