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Cocaine self-administration. A–C, Number of infusions and lever presses over 10 d of self-administration. Cued optimal animals achieved more infusions and made more response for cocaine than other groups. All rats decreased responding on the inactive lever over the 10 sessions. D–F, Total number of infusions and lever presses for intravenous saline. Responding for saline decreased over time. Data are mean ± SEM.
