Subdiaphragmatic vagotomy does not block intraperitoneal lipopolysaccharide-induced fever

Several recent findings, including the inability of subdiaphragmatic vagoto my to block lipopolysaccharide (LPS)-induced interleukin-1 beta (IL-1 beta) protein in brain, have made it necessary to reexamine the role of the subd iaphragmatic vagal afferents in immune-to-brain communication. In this stud y, we examined the effects of intraperitoneal (i.p.) injections of LPS on c ore body temperature in control and subdiaphragmatically vagotomized rats. Vagotomized and sham-operated male Sprague-Dawley rats were injected i.p. w ith vehicle (pyrogen-free saline) on the control day and LPS (1, 10 or 50 m ug/kg) an the experimental day, and core body temperature was monitored by telemetry for 6 h after the injection. At this time, rats were sacrificed, and serum, liver, and pituitary samples were collected. The i.p. injection of LPS increased core body temperature in both sham-operated and vagotomize d rats compared to the saline injection. In addition, LPS significantly inc reased IL-1 beta levels in serum, Liver, and pituitary compared to saline-i njected controls. There were no significant differences in the magnitude of the fever or in the levels of IL-1 beta in serum, liver, or pituitary betw een sham-operated and vagotomized rats. Thus, the current data indicate tha t, at the doses tested, subdiaphragmatic vagal afferents are not crucial fo r i.p. LPS-induced fever. Because several effects of vagotomy have been sho wn to be dependent on dose, we are currently investigating whether vagal af ferents are involved in lower-dose i.p. LPS-induced fever. (C) 2000 Elsevie r Science B.V. All rights reserved.