Effects of bacterial lipopolysaccharide on central monoamines and fever in the rat: involvement of the vagus

Lipopolysaccharide (LPS) is known to produce a number of central and neuroendocrine effects but the mechanisms involved are still unclear. This study was done to investigate the possibility that LPS-induced fever and activation of central monoamines are mediated through the vagus. Adult male rats were subjected to sub-diaphragmatic vagotomy (SDV), or sham operation and treated with saline or LPS in saline (10 μg/kg bw) 2 h later. Rectal temperature was monitored at half-hourly intervals for 5 h after which the animals were sacrificed and monoamine concentrations in hypothalamic nuclei were measured using HPLC-EC. SDV delayed the rise in rectal temperature induced by LPS by 1 h when compared to Sham animals. It also increased the concentrations of monoamines in the paraventricular nucleus of both Sham and SDV rats. This indicates that routes other than the vagus probably mediate LPS’ actions on the central nervous system.