In order to assess the role of vagal nerve afferents in the decrease in food-motivated behavior induced by proinflammatory cytokines, the effects of lipopolysaccharide (LPS, 400 micrograms/kg ip) and recombinant human interleukin-1 beta (IL-1, 750-1500 ng/mouse ip) were tested on nose poke for food in vagotomized and sham-operated mice. Subdiaphragmatic vagotomy attenuated the decrease in response rate induced by IL-1 and LPS. These results suggest that the peripheral immune message is transmitted to the brain via a neural rather than a humoral pathway.