Weakened [corrected] taste-LPS association during endotoxin tolerance.
In naive individuals, the administration of bacterial lipopolysaccharide (LPS) provokes a rapid systemic increase in pro-inflammatory cytokines such as tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta and IL-6, inducing an acute phase response including sickness behavior. Strong associative learning occurs when relevant gustatory/olfactory stimuli precede the activation of the immune system, affecting long-term individual food selection and nutritional strategies. Repeated LPS administration results in the development of an endotoxin tolerance status, characterized by a drastic reduction in the LPS-induced cytokine response. Here we investigated how the postprandial categorization of a relevant taste (0.2% saccharin) changed after administration of a high dose of LPS (0.5 mg/kg i.p.) in LPS-tolerant animals. Determination of the consummatory fluid intake revealed that, in contrast to LPS-naive rats, taste-LPS association did not occur during endotoxin tolerance. Ninety minutes after the single association trial, the plasma responses of TNF-alpha, IL-1beta and IL-6 were completely blunted in LPS-tolerant animals, which also resulted in low LPS-adipsogenic and LPS-anorexic effects. These findings indicate that an identical immune challenge can result in completely different neuro-behavioral consequences depending on the immune history of the individual, thus revealing part of the complex interconnection between the immune and neuro-endocrine systems in regulating food selection and consumption during the infectious process.
Pacheco-Lopez
G
G
Chair of Psychology and Behavioral Immunobiology, Institute for Behavioral Sciences, ETH Zurich, 8092 Zurich, Switzerland. pacheco@ifc.gess.ethz.ch
Niemi
M-B
MB
Engler
H
H
Engler
A
A
Riether
C
C
Doenlen
R
R
Espinosa
E
E
Oberbeck
R
R
Schedlowski
M
M
D000704:Analysis of Variance; D000818:Animals; D001245:Association Learning / Q000502:physiology*; D003214:Conditioning, Classical / Q000502:physiology; D004327:Drinking Behavior / Q000502:physiology; D005247:Feeding Behavior / Q000502:physiology*; D053583:Interleukin-1beta / Q000097:blood; D015850:Interleukin-6 / Q000097:blood; D008070:Lipopolysaccharides / Q000276:immunology*; D008297:Male; D015213:Neuroimmunomodulation / Q000276:immunology / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D012803:Sick Role; D013649:Taste / Q000276:immunology / Q000502:physiology*; D014409:Tumor Necrosis Factor-alpha / Q000097:blood
D053583:Interleukin-1beta; D015850:Interleukin-6; D008070:Lipopolysaccharides; D014409:Tumor Necrosis Factor-alpha