title: Dose-dependent effects of endotoxin on neurobehavioral functions in humans.
abstract: Clinical and experimental evidence document that inflammation and increased peripheral cytokine levels are associated with depression-like symptoms and neuropsychological disturbances in humans. However, it remains unclear whether and to what extent cognitive functions like memory and attention are affected by and related to the dose of the inflammatory stimulus. Thus, in a cross-over, double-blind, experimental approach, healthy male volunteers were administered with either placebo or bacterial lipopolysaccharide (LPS) at doses of 0.4 (n = 18) or 0.8 ng/kg of body weight (n = 16). Pro- and anti-inflammatory cytokines, norephinephrine and cortisol concentrations were analyzed before and 1, 1.75, 3, 4, 6, and 24 h after injection. In addition, changes in mood and anxiety levels were determined together with working memory (n-back task) and long term memory performance (recall of emotional and neutral pictures of the International Affective Picture System). Endotoxin administration caused a profound transient physiological response with dose-related elevations in body temperature and heart rate, increases in plasma interleukin (IL)-6, IL-10, tumor necrosis factor (TNF)-α and IL-1 receptor antagonist (IL-1ra), salivary and plasma cortisol, and plasma norepinephrine. These changes were accompanied by dose-related decreased mood and increased anxiety levels. LPS administration did not affect accuracy in working memory performance but improved reaction time in the high-dose LPS condition compared to the control conditon. In contrast, long-term memory performance was impaired selectively for emotional stimuli after administration of the lower but not of the higher dose of LPS. These data suggest the existence of at least two counter-acting mechanisms, one promoting and one inhibiting cognitive performance during acute systemic inflammation.
authors.affiliation: Institute of Medical Psychology and Behavioral Immunobiology, University of Duisburg-Essen, Essen, Germany.
authors.forename: Jan-Sebastian
authors.initials: JS
authors.lastname: Grigoleit
authors.forename: Jennifer S
authors.initials: JS
authors.lastname: Kullmann
authors.forename: Oliver T
authors.initials: OT
authors.lastname: Wolf
authors.forename: Florian
authors.initials: F
authors.lastname: Hammes
authors.forename: Alexander
authors.initials: A
authors.lastname: Wegner
authors.forename: Stephanie
authors.initials: S
authors.lastname: Jablonowski
authors.forename: Harald
authors.initials: H
authors.lastname: Engler
authors.forename: Elke
authors.initials: E
authors.lastname: Gizewski
authors.forename: Reiner
authors.initials: R
authors.lastname: Oberbeck
authors.forename: Manfred
authors.initials: M
authors.lastname: Schedlowski
mesh_terms: D000328:Adult; D001288:Attention; D001519:Behavior / Q000187:drug effects*; D015992:Body Mass Index; D001831:Body Temperature; D001835:Body Weight; D018592:Cross-Over Studies; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D004731:Endotoxins / Q000378:metabolism* / Q000494:pharmacology; D006339:Heart Rate; D006801:Humans; D007249:Inflammation; D053590:Interleukin 1 Receptor Antagonist Protein / Q000378:metabolism; D016753:Interleukin-10 / Q000097:blood; D015850:Interleukin-6 / Q000097:blood; D008070:Lipopolysaccharides / Q000378:metabolism; D008297:Male; D008568:Memory; D008959:Models, Neurological; D010919:Placebos; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D004731:Endotoxins; D053590:Interleukin 1 Receptor Antagonist Protein; D015850:Interleukin-6; D008070:Lipopolysaccharides; D010919:Placebos; D014409:Tumor Necrosis Factor-alpha; D016753:Interleukin-10