Effect of interleukin-1β on subdiaphragmatic vagal efferents in the rat

Interleukin-1β (IL-1β) is an important mediator of fever and illness. Recent studies have demonstrated that IL-1β (2 μg kg−1) increases gastric vagal afferent activity. The peripheral mechanisms of the action of lower doses were studied by recording the mass efferent and afferent activity of the gastric branch of the ventral vagal nerve in anesthetized rats. Twenty min after i.v. administration of IL-1β (1 μg kg−1) the efferent activity of the vagal nerve was decreased to 62±6% in totally but not in partly vagotomized rats. Preadministration of indomethacin (5 mg kg−1) 30 min before IL-1β blocked this reduction. Administration of 1 μg kg−1 of IL-1β had no effect on the afferent activity of the gastric branch of the vagal nerve. The present results suggest that the subdiaphragmatic vagal afferents modulate the parasympathetic efferent outflow in response to IL-1β partly through prostaglandin dependent mechanisms and that supradiaphragmatic afferents or central sites are more sensitive to the low doses of IL-1β which becomes evident after elimination of the subdiaphragmatic vagal input.