Amphetamine-induced place preference in humans

Abstract

Background: The conditioned place preference procedure is a widely used animal model of rewarding drug effects that, to date, has not been tested in humans. In this study, we sought to demonstrate that humans, like nonhumans, would exhibit a preference for a place previously associated with amphetamine. Further, we investigated the relationship between conditioned place preference and the mood-altering effects of the drug.

Methods: Thirty-one healthy individuals participated in a five-session procedure during which they experienced the effects of d-amphetamine (20 mg) or placebo on two occasions in two distinctive environments (sessions 1-4). One group of subjects (paired group, n = 19) received amphetamine consistently in one room and placebo in another room, whereas a second group (unpaired group, n = 12) received amphetamine and placebo without regard to room. During the sessions, participants completed questionnaires to rate their mood. On the fifth session, they rated their preference for the two rooms.

Results: Individuals in the paired group rated their liking of the amphetamine-paired room significantly higher than the placebo-associated room, whereas there was no difference between ratings of the two rooms for individuals in the unpaired group. In the paired group, drug-liking ratings during the conditioning sessions positively predicted preference for the drug-associated room, whereas reports of amphetamine-induced anxiety and dysphoria negatively predicted room-liking scores.

Conclusions: This study demonstrates that humans, like nonhumans, prefer a place associated with amphetamine administration. These findings support the idea that subjective responses to a drug contribute to its ability to establish place conditioning.

Figure 1

Effects of conditioning upon VAS Room Liking scores. Data represent mean ± SEM room liking for (1) placebo- and drug-paired rooms among individuals in the paired conditioning groups and (2) Room 1 and Room 2 among individuals in the unpaired conditioning group.

Figure 2

Partial regression plots showing correlations between room liking and subjective responses to amphetamine among individuals in the paired groups.