Paradoxical aversive conditioning with ethanol.

In three experiments with hooded rats, paired injections of ethanol and lithium chloride produced an aversion to the taste of ethanol, yet reduced ethanol's potency as an unconditioned stimulus during subsequent taste aversion conditioning with saccharin (i.e., saccharin leads to ethanol). Two of the experiments were designed to test an associative "blocking" account of the latter finding. In each of these experiments, an attempt was made to extinguish the aversion conditioned to a potential blocking stimulus after ethanol-lithium pairings, but before saccharin-ethanol conditioning. Nonreinforced exposure to intraperitoneally mediated ethanol taste cues did not eliminate the detrimental effect of ethanol-lithium pairings on subsequent saccharin-ethanol conditioning (Experiment 2), whereas nonreinforced exposure to handling-injection cues did (Experiment 3), thus providing support for the associative blocking interpretation. Implications of these findings for chemical aversion therapy are discussed.