title: Anxiogenic effect of subclinical bacterial infection in mice in the absence of overt immune activation.
abstract: Challenge of animals with infectious microorganisms is well documented to affect a number of behavioral measures through activation of immune-neural mechanisms. In the present study, the ability of an infectious microorganism to directly alter behavioral responses in the absence of an overt immunologic response was examined. Eight-week-old CF-1 male mice were infected orally with the Gram-negative pathogen Campylobacter jejuni in order to establish a subclinical infection that did not result in immune activation. Microbiological examination of cecal contents revealed the presence of C. jejuni in all infected, but not control, animals 1 and 2 days post-oral challenge. Measurement of interleukin-6 (IL-6) levels and peripheral blood leukocyte populations did not reveal the activation of an overt immune response in 1 or 2 day infected animals as compared to controls. Infected mice demonstrated altered levels of anxiety-like behaviors on the elevated plus-maze as compared to controls on Day 2, but not Day 1, as reflected by a significant decrease in exploratory and an increase in nonexploratory behaviors. The anxiogenic effect of a subclinical infection in the absence of an overt immunologic response suggests that the direct activation of neural pathways by microorganisms may play a role in behavior.
authors.affiliation: Department of Surgery, Minneapolis Medical Research Foundation, MN 55404, USA. MOL13@msus1.msus.edu
authors.forename: M
authors.initials: M
authors.lastname: Lyte
authors.forename: J J
authors.initials: JJ
authors.lastname: Varcoe
authors.forename: M T
authors.initials: MT
authors.lastname: Bailey
mesh_terms: D000818:Animals; D001007:Anxiety / Q000523:psychology*; D001522:Behavior, Animal / Q000502:physiology; D002169:Campylobacter Infections / Q000276:immunology / Q000523:psychology*; D016123:Campylobacter jejuni; D015850:Interleukin-6 / Q000097:blood; D007958:Leukocyte Count; D018655:Lymphocyte Count; D008297:Male; D051379:Mice; D051381:Rats
chemical_list: D015850:Interleukin-6