Bacterial translocation across the intestinal mucosal barrier leads to a macrophage mediated inflammatory response, visceral hyperalgesia and ileus. Our aim was to examine how mediators released into mesenteric lymph following lipopolysaccharide (LPS) treatment influence intestinal afferent sensitivity and the role played by prostanoids in any sensitization. Intestinal lymph was collected from awake rats following treatment with either saline or LPS (5mg/kg, i.p.). Extracellular multiunit afferent recordings were made from paravascular mesenteric nerve bundles supplying the rat jejunum in vitro following arterial administration of control lymph, LPS lymph and LPS. Mesenteric afferent discharge (AD) increased significantly after LPS lymph compared to control lymph. Peak discharge occurred within 2 min and remained elevated for 5 to 8 min. This response was attenuated by pre-treatment with naproxen (10µM), and restored upon addition of prostaglandin E₂ (5µM) in the presence of naproxen, but AH6809 (5µM), a EP₁/ EP₂ receptors antagonist, failed to decrease the magnitude of LPS lymph-induced response. LPS itself also stimulated mesenteric afferent discharge but was unaffected by naproxen. TNF was significantly increased in LPS lymph compared to control lymph (1583 ± 197 vs 169 ± 38 pg/ml, P<0.01) but exogenous TNF failed to evoke any afferent nerve discharge. We concluded that, inflammatory mediators released from the gut into mesenteric lymph during endotoxemia have a profound effect on afferent discharge. These mediators influence afferent firing via the release of local prostaglandins.