On basis of experiments with subdiaphragmatic vagotomy or intraperitoneal capsaicin desensitisation of chemo- and mechano-receptors, in the pathogenesis of endotoxin (LPS)-induced fever a role for abdominal afferent vagal fibres has been proposed. Mainly the monophasic fever to small LPS doses, corresponding to the early part of the usual biphasic fever, was inhibited. In fever, chemo-sensitive signals may originate from cytokines produced by the Kupffer cells upon LPS challenge, while similar chemo- or mechano-sensitive signals may normally be related to the feeding process. In the present experiments fever course was observed following selective gastric, celiac, or hepatic vagotomies. It was found that only the hepatic vagotomy inhibited fever significantly. In other studies the metabolic and thermoregulatory changes of rats were examined following fasting and refeeding. Fasting resulted in a decrease of resting metabolic rate and core temperature, due probably not to substrate deficiency, rather to a regulatory depression. The depression was promptly reversible upon refeeding with either normal or calorie-free (Ca-phosphate with saccharine) food mixtures, suggesting a role for chemo- and mechano-receptors in the depression and its reversal.