Conditioned antisickness: indirect evidence from rats and direct evidence from ferrets that conditioning alleviates drug-induced nausea and emesis.

In a direct test of conditioned antisickness (CAS; B. T. Lett, 1983) theory, the authors measured emesis in ferrets and found those with a history of forward pairings of pentobarbital and lithium to have fewer and shorter bouts of emesis on test, whether induced by lithium or, in a subsequent test, by the highly emetogenic anticancer drug cisplatin. In an indirect test of her CAS theory, B. T. Lett (1992) paired interoceptive (drug) or place cues with lithium chloride toxicosis and found that rats with a forward-pairings history ate less food than controls on a forward-pairing test, consistent with conditioned sickness rather than CAS. But rats eat dirt or clay in response to sickness and adaptively eat small amounts of food when clay is not available. We substituted clay (kaolin) for food in a partial procedural replication of B. T. Lett's (1992, Experiment 1) experiment and found that rats with a history of forward pairings of pentobarbital and lithium ate less kaolin, which is consistent with CAS.