Central activation of the cholinergic anti-inflammatory pathway reduces surgical inflammation in experimental post-operative ileus

BACKGROUND AND PURPOSE Electrical stimulation of the vagus nerve reduces intestinal inflammation following mechanical handling, thereby shortening post-operative ileus in mice. Previous studies in a sepsis model showed that this cholinergic anti-inflammatory pathway can be activated pharmacologically by central administration of semapimod, an inhibitor of p38 mitogen-activated protein kinase. We therefore evaluated the effect of intracerebroventricular (i.c.v.) semapimod on intestinal inflammation and post-operative ileus in mice. EXPERIMENTAL APPROACH Mice underwent a laparotomy or intestinal manipulation 1 h after i.c.v. pre-treatment with semapimod (1 mu g center dot kg-1) or saline. Drugs were administered through a cannula placed in the left lateral ventricle 1 week prior to experimentation. Twenty-four hours after surgery, gastric emptying was measured using scintigraphy, and the degree of intestinal inflammation was assessed. Finally, activation of brain regions was assessed using quantitative immunohistochemistry for c-fos. KEY RESULTS Intestinal manipulation induced inflammation of the manipulated intestine and significantly delayed gastric emptying, 24 h after surgery in saline-treated animals. Semapimod significantly reduced this inflammation and improved gastric emptying. Vagotomy enhanced the inflammatory response induced by intestinal manipulation and abolished the anti-inflammatory effect of semapimod. Semapimod but not saline induced a significant increase in c-fos expression in the paraventricular nucleus, the nucleus of the solitary tract and the dorsal motor nucleus of the vagus nerve. CONCLUSIONS AND IMPLICATIONS Our findings show that i.c.v. semapimod reduces manipulation-induced intestinal inflammation and prevented post-operative ileus. This anti-inflammatory effect depends on central activation of the vagus nerve.