Amphetamine-induced enhancement of responding for conditioned reward in rats: interactions with repeated testing.
BACKGROUND
The mesolimbic dopamine system underlies the ability of reward-related stimuli to control operant behavior. Previous work has shown that amphetamine potentiates operant responding for conditioned rewards (CRs).


OBJECTIVE
Here, we asked whether the profile of this amphetamine-produced potentiation changes with repeated CR presentation, i.e., as the CR is being extinguished.


METHODS
Amphetamine (0-1.0 mg/kg, i.p.), administered over four daily sessions using a Latin square design, dose-dependently increased lever pressing for a 'lights-off' stimulus previously paired with food in rats.


RESULTS
The amphetamine-produced enhancement of responding for CR was significantly modulated with repeated CR exposure: it was strongest on day 1 and became less pronounced in subsequent sessions whereas the CR effect persisted. In further experiments, rats receiving LiCl devaluation of the primary reward failed to show a significant reduction in the amphetamine-produced enhancement of responding for CR.


CONCLUSIONS
The nature of the dissociable effects of amphetamine on responding for CR versus the CR effect itself remains to be elucidated.
Department of Psychology, Queen's University, Kingston, ON, K7L 3N6, Canada. tvg3@le.ac.uk
Todor V
TV
Gerdjikov
Tyson W
TW
Baker
Richard J
RJ
Beninger
D000661:Amphetamine / Q000494:pharmacology*; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D003216:Conditioning, Operant / Q000187:drug effects*; D003627:Data Interpretation, Statistical; D004305:Dose-Response Relationship, Drug; D008297:Male; D009483:Neuropsychological Tests; D051381:Rats; D017208:Rats, Wistar; D012201:Reward; D013997:Time Factors
D000661:Amphetamine