Lithium-induced context aversion in rats as a model of anticipatory nausea in humans.

In three experiments, rats received injections of lithium chloride (LiCl) before being exposed to a distinctive context. In a subsequent test, rats given access to sucrose solution in this context consumed less than control subjects given sucrose in another context that had been paired with a saline injection (Experiment 1), or was quite novel (Experiment 2). Experiment 3 demonstrated that a context that had been associated with LiCl would serve to block the acquisition of a conditioned flavor aversion when it was presented immediately after the injection on a flavor-LiCl trial. These results show that a procedure in which rats experience the adverse effects of a lithium injection in the presence of contextual cues is effective in endowing those cues with aversive properties. It is argued that the context evokes a state of conditioned nausea, and the parallel with the clinical phenomenon of anticipatory nausea and vomiting (ANV) in human patients is outlined.