Journal
PHARMACOLOGY BIOCHEMISTRY AND BEHAVIOR
Volume 93, Issue 3, Pages 343-348Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.pbb.2009.05.013
Keywords
Cocaine; Escalation; Delay discounting; Impulsivity; Rats
Funding
- NIDA NIH HHS [K05 DA015267-07, K05 DA015267, R01 DA003240-25, F31 DA023301-02, R01 DA003240, F31 DA 023301-02, F31 DA023301, R01 DA 003240-25] Funding Source: Medline
- PHS HHS [K05 015267-07] Funding Source: Medline
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Impulsivity, as measured by the delay-discounting task, predicts the acquisition of cocaine self-administration and reinstatement of cocaine seeking in rats. The purpose of this study was to extend these results to the escalation phase of drug self-administration. Female rats were initially screened for high (Hil) or low (Lol) impulsivity for food reinforcement using a delay-discounting procedure. They were then implanted with i.v. catheters and trained to lever press for cocaine infusions (0.8 mg/kg). Once cocaine intake stabilized, rats were allowed to self-administer cocaine (0.4 mg/kg) under a fixed-ratio 1 (FR 1) schedule during three, 2 h short-access sessions. Subsequently, performance was briefly assessed under a progressive ratio (PR) schedule for 3 doses of cocaine (0.2, 0.8,and 3.2 mg/kg). Following PR testing, the cocaine dose was then changed to 0.4 mg/kg. Session length was then extended to 6 h for 21 days (extended access),and 0.4 mg/kg cocaine was available under a FR 1 schedule. After the 21-day extended access phase, responses and infusions under the short access FR and PR dose-response conditions were reassessed. The results indicated that Hit rats escalated cocaine-reinforced responding during the extended access condition, but Lot rats did not. Hit rats also earned significantly more infusions than Lot rats under the post-escalation short access FR condition. However, Hit and Lot rats did not differ under the pre- and post-extended access PR conditions. This study suggests that individual differences in impulsivity predict escalation of cocaine self-administration in female rats, which may have implications in the prediction of binge-like patterns of cocaine intake in women. (C) 2009 Elsevier Inc. All rights reserved.
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