Strategies for understanding the pharmacological effects of ethanol with drug discrimination procedures.

Ethanol appears to produce a stimulus complex, or compound cue, composed of distinct components that are mediated by different receptor systems. In ethanol vs. water discriminations, it appears that ethanol produces a redundant stimulus complex such that separate, receptor-mediated activity can serve as the basis for the discrimination. These discriminations have been termed redundant, because multiple features of the cue could serve as the basis of the discrimination. In ethanol vs. water discriminations, one common feature is the asymmetrical generalizations between components of the ethanol cue and ethanol. There is also evidence for overshadowing of one component by other components of the ethanol stimulus complex. It appears possible to transfer the basis of the ethanol cue from a redundant cue to a conditional cue with specific training procedures. When the discriminative stimulus effects of ethanol are juxtoposed with those of one component of the ethanol complex, as in ethanol vs. water vs. pentobarbital discriminations, the ethanol discrimination shifts to a conditional basis. The ability to antagonize an ethanol discrimination may be dependent upon whether the discrimination is based on redundant component stimuli or conditional presence of all component stimuli.