Journal
PHARMACOLOGY BIOCHEMISTRY AND BEHAVIOR
Volume 73, Issue 3, Pages 663-671Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/S0091-3057(02)00853-5
Keywords
alternative reinforcer; cocaine; exercise; intravenous; rat; self-administration; sex; substitution; wheel-running
Funding
- NIAAA NIH HHS [F31 AA005575] Funding Source: Medline
- NIDA NIH HHS [R37 DA03240] Funding Source: Medline
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This experiment examines the effect of access to a running-wheel on intravenous cocaine self-administration in male and female rats. Rats maintained at 85% of their free-feeding body weight were first exposed to the running-wheel alone during the 6-h sessions until behavior stabilized for 14 days. Intravenous cannulae were then implanted, and the rats were trained to self-administer a low dose of cocaine (0.2 mg/kg) under a fixed-ratio (FR 1) schedule during the 6-h sessions, while the wheel remained inactive and cocaine self-administration stabilized (cocaine-only condition). Next, the wheel access and cocaine self-administration were concurrently available followed by a period of cocaine-only. Behavior was allowed to stabilize for 10 days at each phase. During wheel access, cocaine infusions decreased by 21.9% in males and 70.6% in females compared to the cocaine-only condition; the effect was statistically significant in females. Infusions increased to baseline levels when wheel access was terminated. When cocaine infusions were concurrently available, wheel revolutions were reduced by 63.7% and 61.5% in males and females, respectively, compared to the wheel-only condition. This result did not differ due to sex, but it was statistically significant when data from males and females were combined. These results indicate that wheel-running activity had a greater suppressant effect on cocaine self-administration in females than in males, and in females, wheel-running and cocaine self-administration are substitutable as reinforcers. (C) 2002 Elsevier Science Inc. All rights reserved.
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