The discriminative stimulus effects of a cocaine-alcohol combination

Despite the toxic effects of concurrent cocaine and alcohol use, the combination is widely co-used. One possible reason for this co-use is that the combination produces a stimulus which is perceived as different from, or perhaps more rewarding than, either of its parent components. To assess the nature of the combination's subjective effects, the present experiment examined the combination in female Long-Evans rats with a drug discrimination procedure. Generalization tests were performed to assess the level of combination-appropriate responding to various doses of cocaine, alcohol, cocaethylene and morphine. Although cocaine and alcohol administered alone produced combination-appropriate responding in a dose-dependent manner, stimulus control at the training doses, when summed, did not add up to the combination-appropriate responding produced by the drug combination. Cocaethylene and morphine failed to substitute fully for the training mixture. These results suggest that the subjective effects produced by the combination are qualitatively different from those produced by its component elements.