期刊
PSYCHOPHARMACOLOGY
卷 178, 期 2-3, 页码 193-201出版社
SPRINGER
DOI: 10.1007/s00213-004-1994-4
关键词
cocaine; delay-discounting; food; fixed-ratio; impulsivity; rats; self-administration
资金
- NIDA NIH HHS [K05 DA15267, R01 DA03240, R03 DA13575-01] Funding Source: Medline
Rationale: Previous research in humans suggests a relationship between drug abuse and impulsivity as shown by selection of a smaller immediate reward over a larger delayed reward. However, it is not clear whether impulsivity precedes drug abuse or drug abuse influences impulsivity. Objective: The hypothesis of the present experiment was that rats selected for choosing smaller, immediate over larger, delayed food would acquire IV cocaine self-administration faster than those choosing larger, delayed food rewards. Methods: Female rats were screened for locomotor activity and trained on a delay discounting procedure that allowed them access to two response levers and a food pellet dispenser. Under a fixed-ratio (FR) 1 schedule, responding on one lever resulted in immediate delivery of one 45 mg pellet, while responding on the other lever resulted in delivery of three 45 mg pellets after a variable delay that increased after responses on the delay lever and decreased after responses on the immediate lever. For each rat, a mean adjusted delay (MAD) was calculated for each daily session, and stability was defined as MADs varying less than 5 s across 5 days. Based on their average MADs, rats were separated into low impulsive (LoI) and high impulsive (HiI) groups, implanted with an indwelling IV catheter, and trained to lever press for cocaine ( 0.2 mg/kg) under an FR1 schedule. Results: There were no differences in locomotor activity between the LoI and HiI groups; however, a greater percentage of the HiI group acquired cocaine self-administration, and they did so at a significantly faster rate than the LoI rats. Conclusions: Performance on the delay discounting model of impulsivity predicted vulnerability to subsequent acquisition of cocaine self-administration.
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