SUBDIAPHRAGMATIC VAGOTOMY BLOCKS INDUCTION OF IL-1-BETA MESSENGER-RNAIN MICE BRAIN IN RESPONSE TO PERIPHERAL LPS

To test the possibility that the vagus nerve is involved in the commun ication between the immune system and the brain, we injected sham-oper ated and vagotomized mice with physiological saline or lipopolysacchar ide (LPS; 400 mu g/kg ip). Vagotomy attenuated LPS-induced depression of general activity measured 2 h after treatment but did not alter the increase in plasma levels of IL-1 beta in response to LPS. In additio n, vagotomy abrogated the LPS-induced increase in the levels of transc ripts for IL-1 beta, as determined by semiquantitative polymerase chai n reaction after reverse transcription, in the hypothalamus and hippoc ampus, but not in the pituitary of vagotomized mice. This relationship between the effects of vagotomy on the behavioral effects of LPS and the LPS-induced brain expression of IL-1 beta mRNA indicates that vaga l afferent fibers play a prominent role in the pathways of communicati on between the immune system and the brain.