title: Lipopolysaccharide inhibits the simultaneous establishment of LiCl-induced anticipatory nausea and intravascularly conditioned taste avoidance in the rat.
abstract: This study examined the effects of the bacterial endotoxin, lipopolysaccharide (LPS), on the establishment of anticipatory nausea and conditioned taste avoidance in a simultaneous conditioning paradigm using an intravascular/intraperitoneal saccharin taste. 83 naïve adult male Long-Evans rats were injected (intraperitoneal) with either 200 μg/kg LPS or 0.9% saline (NaCl), 90 min prior to ip treatment with either 64 mg/kg LiCl, 64 mg/kg LiCl+2.0% saccharin, 0.9% NaCl, or 0.9% NaCl+2.0% saccharin, and immediately placed into a distinctive context for 30 min (repeated over 4 conditioning days, spaced 72 h apart). 72 h following the final conditioning day, each animal was re-exposed to the context on a drug-free test day where orofacial responding was recorded. The next day, animals received a 24 h 2-bottle preference test with a choice between water and a palatable 0.2% saccharin solution. Results showed that LPS exposure, prior to LiCl or LiCl+Saccharin treatment, inhibited the establishment of anticipatory nausea, as evidenced by significantly lower conditioned gaping frequencies relative to animals pre-treated with NaCl followed by LiCl or LiCl+Saccharin. LPS pre-treatment also inhibited the formation of LiCl-induced taste avoidance, as evidence by significantly higher saccharin preferences in Group LPS-LiCl+Saccharin relative to Group NaCl-LiCl+Saccharin. The results of the current study provide additional evidence for the deleterious effects of LPS on learning and memory in aversive conditioning.
authors.affiliation: Department of Psychology, University of Western Ontario, London, Ontario, Canada N6A 5C2. cclouti@uwo.ca
authors.forename: Caylen J
authors.initials: CJ
authors.lastname: Cloutier
authors.forename: Martin
authors.initials: M
authors.lastname: Kavaliers
authors.forename: Klaus-Peter
authors.initials: KP
authors.lastname: Ossenkopp
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D059031:Anticipation, Psychological / Q000187:drug effects*; D001362:Avoidance Learning / Q000187:drug effects*; D001522:Behavior, Animal / Q000187:drug effects; D001835:Body Weight / Q000187:drug effects; D005145:Face / Q000502:physiology; D005239:Fear / Q000523:psychology; D008070:Lipopolysaccharides / Q000494:pharmacology*; D018021:Lithium Chloride; D008297:Male; D009055:Mouth / Q000502:physiology; D009325:Nausea / Q000139:chemically induced* / Q000523:psychology*; D051381:Rats; D020318:Rats, Long-Evans; D012439:Saccharin / Q000494:pharmacology; D013549:Sweetening Agents / Q000494:pharmacology; D013649:Taste / Q000187:drug effects*
chemical_list: D008070:Lipopolysaccharides; D013549:Sweetening Agents; D012439:Saccharin; D018021:Lithium Chloride