Perturbations in different forms of cost/benefit decision making induced by repeated amphetamine exposure.
BACKGROUND
Psychostimulant abuse has been linked to impairments in cost-benefit decision making.


OBJECTIVE
We assessed the effects of repeated amphetamine (AMPH) treatment in rodents on two distinct forms of decision making.


METHODS
Separate groups of rats were trained for 26 days on either a probabilistic (risk) or effort-discounting task, each consisting of four discrete blocks of ten choice trials. One lever always delivered a smaller reward (one or two pellets), whereas another lever delivered a four-pellet reward. For risk-discounting, the probability of receiving the larger reward decreased across trial blocks (100-12.5%), whereas on the effort task, four pellets could be obtained after a ratio of presses that increased across blocks (2-20). After training, rats received 15 saline or AMPH injections (escalating from 1 to 5 mg/kg) and were then retested during acute and long-term withdrawal.


RESULTS
Repeated AMPH administration increased risky choice 2-3 weeks after drug exposure, whereas these treatments did not alter effort-based decision making in a separate group of animals. However, prior AMPH exposure sensitized the effects of acute AMPH on both forms of decision making, whereby lower doses were effective at inducing "risky" and "lazy" patterns of choice.


CONCLUSIONS
Repeated AMPH exposure leads to relatively long-lasting increases in risky choice, as well as sensitization to the effects of acute AMPH on different forms of cost/benefit decision making. These findings suggest that maladaptive decision-making processes exhibited by psychostimulant abusers may be caused in part by repeated drug exposure.
Department of Psychology and Brain Research Center, University of British Columbia, 2136 West Mall, Vancouver, BC V6T1Z4, Canada. floresco@psych.ubc.ca
Stan B
SB
Floresco
Jennifer M
JM
Whelan
D000661:Amphetamine / Q000494:pharmacology*; D019969:Amphetamine-Related Disorders / Q000503:physiopathology*; D000704:Analysis of Variance; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D000697:Central Nervous System Stimulants / Q000494:pharmacology*; D003216:Conditioning, Operant / Q000187:drug effects; D003657:Decision Making / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D008297:Male; D011336:Probability; D051381:Rats; D020318:Rats, Long-Evans; D012055:Reinforcement Schedule; D012201:Reward; D013997:Time Factors
D000697:Central Nervous System Stimulants; D000661:Amphetamine