Exposure to a lithium-paired context elicits gaping in rats: A model of anticipatory nausea.

Chemotherapy patients report anticipatory nausea and vomiting upon re-exposure to the cues previously associated with the treatment. Although rats do not vomit, they display a distinctive gaping reaction when exposed to a toxin-paired flavored solution. Here we report that rats also display gaping reactions during exposure to a context previously paired with the illness-inducing effects of lithium chloride (Experiment 1). This gaping reaction is suppressed by pretreatment with the antiemetic agent, Delta 9-tetrahydrocannabinol, but not ondansetron (Experiment 2). The finding that gaping is elicited by an illness-paired context confirms the proposal that an illness-paired context can evoke a conditioned state of nausea and supports the case of context-aversion as a rat model for anticipatory nausea.