Ketamine acts as an internal contextual stimulus that facilitates the retrieval of weak associations in conditioned taste aversion

Abstract Ketamine (6 mg/kg), when injected intraperitoneally into Long-Evans rats during both the acquisition and the test phases, was found to facilitate the retrieval of a conditioned taste aversion (CTA) based on pairings of a flavor with lithium chloride (LiCl). This facilitation was not a monotonic function of LiCl dosage, since it was observed with only 15.90 mg/kg and not 7.95, 31.80, 63.60, or 127.20 mg/kg. In our conditions, 15.90 mg/kg of LiCl is a dosage that elicits a weak CTA. This result suggests that ketamine acts like a contextual cue, which facilitates the retrieval of weak but not of strong associations. This result is discussed in the framework of drug-induced state dependency, and compared with the effects of external contextual cues.