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Pharmacol Biochem Behav. 2011 Sep;99(3):301-6. doi: 10.1016/j.pbb.2011.05.005. Epub 2011 May 11.

Rapid delivery of cocaine facilitates acquisition of self-administration in rats: an effect masked by paired stimuli.

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  • 1Preclinical Pharmacology Section, Behavioral Neuroscience Branch, DHHS/NIH/NIDA Intramural Research Program, 251 Bayview Blvd., Suite 200, Baltimore, MD 21224, USA.


In general, faster infusions of cocaine are more likely to support behavior related to abuse than are slower infusions. However, some studies of cocaine self-administration in rats have failed to support this finding, possibly because the effect was masked by other factors. One such factor may be the pairing of a stimulus with the infusion, a procedure that is known to facilitate acquisition of drug self-administration. We compared fast and slow infusions by allowing groups of rats to acquire cocaine self-administration at a dose of 1mg/kg/infusion, delivered over different durations (1.8 or 100 s). Two groups were trained with either short or long infusions paired with a visual stimulus change (lights off), and two other groups were trained with short or long durations but with no stimulus change. Both groups trained with a paired stimulus acquired cocaine self-administration. With no stimulus change, the rats trained with the 1.8-s infusion acquired cocaine self-administration at a rate comparable to the two groups that were trained with a paired stimulus. However, most rats in the group trained with the 100-s infusion that was not accompanied by a stimulus change failed to acquire cocaine self-administration. The stimulus itself did not support responding. These results indicate that infusing a given dose of cocaine over a longer duration reduces its ability to support self-administration, but drug-paired stimuli can partially mask this effect by enhancing the effectiveness of slow infusions.

Published by Elsevier Inc.

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