Simultaneous conditioning of "gaping" responses and taste avoidance in rats injected with LiCl and saccharin: examining the role of context and taste cues in the rodent model of anticipatory nausea

Abstract

This study examined whether rats can simultaneously learn to associate lithium chloride (LiCl)-induced nausea with both contextual and intravascular taste cues. During the conditioning phase (4 days, 72h apart), 32 male Long Evans rats were injected intraperitoneally with either isotonic saline (NaCl), lithium chloride (LiCl, 127mg/kg), saline plus 2% saccharin (NaCl+Saccharin), or lithium chloride plus 2% saccharin (LiCl+Saccharin) immediately prior to a 30min exposure to a novel context. 72h following the final conditioning day, each animal was re-exposed to the context on a drug-free test day. The next day, animals received a 24h 2-bottle preference test with a choice between water and a palatable saccharin solution. Results showed that animals treated with LiCl during conditioning, with or without saccharin, displayed significantly higher levels of conditioned gaping responses, indicative of nausea, upon re-exposure to the context, relative to NaCl and NaCl+Saccharin controls. Animals administered LiCl+Saccharin during conditioning also displayed significant conditioned taste avoidance to the saccharin solution during the two bottle choice test. These results indicate that systemic administration (intraperitoneal) of a LiCl+Saccharin solution is effective in simultaneously conditioning toxin elicited nausea to both internal (taste) and external (context) cues.