title: Short day lengths attenuate the symptoms of infection in Siberian hamsters.
abstract: Symptoms of infection, such as fever, anorexia and lethargy, are ubiquitous among vertebrates. Rather than nonspecific manifestations of illness, these responses are organized, adaptive strategies that are often critical to host survival. During times of energetic shortage such as winter, however, it may be detrimental for individuals to prolong energetically demanding symptoms such as fever. Individuals may adjust their immune responses prior to winter by using day length to anticipate energetically-demanding conditions. If the expression of sickness behaviours is constrained by energy availability, then cytokine production, fever, and anorexia should be attenuated in infected Siberian hamsters housed under simulated winter photoperiods. We housed hamsters in either long (14 L : 10 D) or short (10 L : 14 D) day lengths and assessed cytokines, anorexia and fever following injections of lipopolysaccharide (LPS). Short days attenuated the response to lipopolysaccharide, by decreasing the production of interleukin (IL)-6 and IL-1beta, and diminishing the duration of fever and anorexia. Short-day exposure in hamsters also decreased the ingestion of dietary iron, a nutrient vital to bacterial replication. Taken together, short day lengths attenuated the symptoms of infection, presumably to optimize energy expenditure and survival outcome.
authors.affiliation: Department of Psychology, The Johns Hopkins University, Baltimore, MD 21218-2686, USA. bilbo.1@osu.edu
authors.forename: Staci D
authors.initials: SD
authors.lastname: Bilbo
authors.forename: Deborah L
authors.initials: DL
authors.lastname: Drazen
authors.forename: Ning
authors.initials: N
authors.lastname: Quan
authors.forename: Lingli
authors.initials: L
authors.lastname: He
authors.forename: Randy J
authors.initials: RJ
authors.lastname: Nelson
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D006224:Cricetinae; D004734:Energy Metabolism / Q000187:drug effects; D004797:Enzyme-Linked Immunosorbent Assay; D005247:Feeding Behavior / Q000187:drug effects; D005334:Fever / Q000139:chemically induced / Q000503:physiopathology*; D007375:Interleukin-1 / Q000096:biosynthesis / Q000276:immunology; D015850:Interleukin-6 / Q000096:biosynthesis / Q000276:immunology; D007501:Iron / Q000008:administration & dosage; D008070:Lipopolysaccharides / Q000276:immunology / Q000494:pharmacology; D008297:Male; D008892:Milk / Q000737:chemistry; D009929:Organ Size / Q000187:drug effects; D017111:Phodopus / Q000502:physiology*; D017440:Photoperiod; D012098:Reproduction; D015431:Weight Loss / Q000187:drug effects
chemical_list: D007375:Interleukin-1; D015850:Interleukin-6; D008070:Lipopolysaccharides; D007501:Iron