S. Lacosta et al., Behavioral and neurochemical consequences of lipopolysaccharide in mice: anxiogenic-like effects, BRAIN RES, 818(2), 1999, pp. 291-303
Systemic administration of lipopolysaccharide (LPS) induces sickness behavi
ors, as well as alterations of hypothalamic-pituitary-adrenal functioning c
ommonly associated with stressors. in the present investigation, it was dem
onstrated that systemic LPS treatment induced a sickness-like behavioral pr
ofile (reduced active behaviors, soporific effects, piloerection, ptosis),
which appeared to be dependent upon the novelty of the environmental contex
t in which animals were tested. As well, LPS induced anxiogenic-like respon
ses, including decreased time spent in the illuminated portion of a light-d
ark box, reduced open-arm entries in a plus-maze test, and decreased contac
t with a novel stimulus object in an open-field situation. The behavioral c
hanges were accompanied by increased plasma ACTH and corticosterone levels.
As well, LPS induced increased turnover of norepinephrine (NE), dopamine (
DA) and serotonin (5-HT) in the paraventricular nucleus (PVN), median emine
nce plus arcuate nucleus, hippocampus, as well as NE turnover within the lo
cus coeruleus and DA turnover within the nucleus accumbens. Although these
neurochemical variations were reminiscent of those elicited by stressors, L
PS was not particularly effective in modifying DA activity within the prefr
ontal cortex or NE within the amygdala, variations readily induced by stres
sors. Whether the LPS-induced anxiogenic-like responses were secondary to t
he illness engendered by the endotoxin remains to be determined. Neverthele
ss, it ought to be considered that bacterial endotoxin challenge, and the e
nsuing cytokine changes, may contribute to emotionality and perhaps even an
xiety-related behavioral disturbances. (C) 1999 Elsevier Science B.V. All r
ights reserved.