Simon NW, Mendez IA, Setlow B. Effects of prior amphetamine exposure on approach strategy in appetitive Pavlovian conditioning in rats.
Psychopharmacology (Berl) 2009;
202:699-709. [PMID:
18850090 PMCID:
PMC7450361 DOI:
10.1007/s00213-008-1353-y]
[Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/21/2008] [Accepted: 09/22/2008] [Indexed: 11/25/2022]
Abstract
RATIONALE
Pavlovian conditioning with a discrete reward-predictive visual cue can elicit two classes of behaviors: "sign-tracking" (approach toward and contact with the cue) and "goal-tracking" (approach toward the site of reward delivery). Sign-tracking has been proposed to be linked to behavioral disorders involving compulsive reward-seeking, such as addiction. Prior exposure to psychostimulant drugs of abuse can facilitate reward-seeking behaviors through enhancements in incentive salience attribution. Thus, it was predicted that a sensitizing regimen of amphetamine exposure would increase sign-tracking behavior.
OBJECTIVE
The purpose of these experiments was to determine how a regimen of exposure to amphetamine affects subsequent sign-tracking behavior.
MATERIALS AND METHODS
Male Long-Evans rats were given daily injections of d-amphetamine (2.0 mg/kg) or saline for 5 days, then given a 7-day drug-free period followed by testing in a Pavlovian conditioning task. In experiment 1, rats were presented with a visual cue (simultaneous illumination of a light and extension of a lever) located either to the left or right of a centrally located food trough. One cue (CS+) was always followed by food delivery, whereas the other (CS-) was not. In experiment 2, rats were tested in a nondiscriminative (CS+ only) version of the task.
RESULTS
In both experiments, amphetamine-exposed rats showed less sign-tracking and more goal-tracking compared to saline controls.
CONCLUSIONS
Contrary to predictions, prior amphetamine exposure decreased sign-tracking and increased goal-tracking behavior. However, these results do support the hypothesis that psychostimulant exposure and incentive sensitization enhance behavior directed toward reward-proximal cues at the expense of reward-distal cues.
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