Antisickness conditioning using a nausea-producing nondrug cue.

Most drugs induce conditioned taste aversions and are therefore commonly supposed to produce nausea or sickness. Paradoxically, some drugs appear to lose induction capability when made to serve as a cue for a second drug that produces more severe sickness, perhaps through selective association with a hypothetical homeostatic or antisickness aftereffect of sickness. Using drug-drug pairings had made antisickness conditioning theory difficult to validate. We report here that rotation serves in lieu of a drug cue in rats. Rotation-drug pairings eliminate drug interactions and enable the sorts of parametric manipulations required to validate the theory. By postulating a common sickness mechanism to explain both taste aversion and aversion failure, the theory places the phenomenon within an adaptive evolutionary framework. Successful application could yield a direct countermeasure to severe nausea in clinical settings.