title: Responding for conditioned reinforcement in C57BL/6 and CD-1 mice, and Sprague-Dawley rats: Effects of methylphenidate and amphetamine.
abstract: BACKGROUND
  Characterization of responding for conditioned reinforcement in mice is important to implement genetic tools in examining the neurobiological mechanisms underlying reward-related learning and incentive motivation.
  
  
  METHODS
  Inbred C57BL/6 mice, outbred CD-1 mice, and outbred Sprague-Dawley rats underwent Pavlovian conditioning in which a conditioned stimulus (CS) was paired with saccharin. Subsequently, subjects were allowed to respond for that CS in tests of responding for conditioned reinforcement. Experiments measured the effects of methylphenidate (MPH) and amphetamine (AMPH) on lever pressing for conditioned reinforcement in mice and rats. We further examined the stability of responding for conditioned reinforcement in mice after repeated testing and the extinction of this behaviour following omission of the reinforcer. We also determined whether the CS exhibited reinforcing properties if it was not paired with saccharin.
  
  
  RESULTS
  C57BL/6 and CD-1 mice learned to respond for a conditioned reinforcer similarly to rats, and the behaviour was stable over time. MPH increased responding in CD-1 mice and rats, but not in C57BL/6 mice. AMPH only increased responding in rats. Responding was reduced following omission of the conditioned reinforcer, and responding was only established when the CS was paired with saccharin.
  
  
  CONCLUSIONS
  These experiments characterize a conditioned reinforcement test which produces stable responding in two different mouse backgrounds. These findings also show that dopaminergic psychomotor stimulants can differently affect rats and mice in tests of responding for conditioned reinforcement.
authors.affiliation: Department of Psychology, University of Toronto, 100 St. George Street, Toronto, ON, M5S 3G3, Canada, caleb.browne@mail.utoronto.ca.
authors.forename: J D Caleb
authors.initials: JD
authors.lastname: Browne
authors.forename: Ashlie D
authors.initials: AD
authors.lastname: Soko
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Fletcher
mesh_terms: D000661:Amphetamine / Q000494:pharmacology*; D000818:Animals; D000697:Central Nervous System Stimulants / Q000494:pharmacology*; D003214:Conditioning, Classical / Q000187:drug effects*; D008297:Male; D008774:Methylphenidate / Q000494:pharmacology*; D051379:Mice; D008810:Mice, Inbred C57BL; D009042:Motivation / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012054:Reinforcement, Psychology; D012439:Saccharin / Q000494:pharmacology
chemical_list: D000697:Central Nervous System Stimulants; D008774:Methylphenidate; D000661:Amphetamine; D012439:Saccharin