title: Single-trial conditioning in a human taste-endotoxin paradigm induces conditioned odor aversion but not cytokine responses.
abstract: Immunological responses to bacterial endotoxin can be behaviorally conditioned in rodents. However, it is unclear whether an acute systemic inflammatory response can be behaviorally conditioned in humans. Thus, in a double-blind placebo-controlled study, 20 healthy, male subjects received either a single injection of lipopolysaccharide (LPS) or saline together with a novel tasting beverage (conditioned stimulus, CS). Five days later, all subjects received a saline injection and were re-exposed to the CS. Blood was drawn prior to as well as 0.5, 1.5, 3, 4, 6, and 24 h after LPS administration or CS re-exposure. Endotoxin administration led to transient increases in plasma concentrations of interleukin (IL)-6, IL-10, and tumor necrosis factor (TNF)-α and to a significant rise in body temperature. Sole presentation of the CS during evocation did induce neither alterations in body temperature nor changes in plasma cytokine levels. However, subjects in the experimental group rated the smell of the CS significantly more aversive compared to the control group. Employing endotoxin as a US in a single trial taste-immune conditioning paradigm in humans shows a behaviorally conditioned smell aversion but no learned alterations in cytokine levels.
authors.affiliation: Institute of Medical Psychology & Behavioral Immunobiology, University Hospital Essen, University of Duisburg-Essen, D-45122 Essen, Germany.
authors.forename: Jan-Sebastian
authors.initials: JS
authors.lastname: Grigoleit
authors.forename: Jennifer S
authors.initials: JS
authors.lastname: Kullmann
authors.forename: Anne
authors.initials: A
authors.lastname: Winkelhaus
authors.forename: Harald
authors.initials: H
authors.lastname: Engler
authors.forename: Alexander
authors.initials: A
authors.lastname: Wegner
authors.forename: Florian
authors.initials: F
authors.lastname: Hammes
authors.forename: Reiner
authors.initials: R
authors.lastname: Oberbeck
authors.forename: Manfred
authors.initials: M
authors.lastname: Schedlowski
mesh_terms: D000328:Adult; D000339:Affect / Q000502:physiology; D001007:Anxiety / Q000503:physiopathology; D001362:Avoidance Learning; D001831:Body Temperature; D003213:Conditioning, Psychological; D016207:Cytokines / Q000097:blood* / Q000502:physiology; D004311:Double-Blind Method; D006801:Humans; D016753:Interleukin-10 / Q000097:blood / Q000502:physiology; D015850:Interleukin-6 / Q000097:blood / Q000502:physiology; D008070:Lipopolysaccharides / Q000494:pharmacology; D008297:Male; D009812:Odorants; D013649:Taste / Q000276:immunology / Q000502:physiology; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha / Q000097:blood / Q000502:physiology
chemical_list: D016207:Cytokines; D015850:Interleukin-6; D008070:Lipopolysaccharides; D014409:Tumor Necrosis Factor-alpha; D016753:Interleukin-10