Effects of afferent and efferent denervation of vagal nerve on endotoxin-induced oxidative stress in rats

This study investigated the role of vagal innervation in oxidative stress after systemic administration of lipopolysaccharide (LPS) endotoxin. Control rats and rats subjected to bilateral subdiaphragmatic vagotomy, perivagal capsaicin application (5 mg/ml) or cholinergic receptor blockade with subcutaneous atropine (1 mg/kg), were intraperitoneally injected with 300 μg/kg of LPS and euthanized 4 h later. Results indicated that; (1) surgical vagotomy and sensory denervation by perivagal capsaicin increased brain oxidative stress and decreased reduced glutathione in basal condition (saline-treated rats) and following endotoxin challenge; (2) oxidative stress decreased after cholinergic blockade with atropine in endotoxemic rats; (3) nitric oxide decreased by abdominal vagotomy, sensory deafferentation and cholinergic blockade after endotoxin injection; (4) liver lipid peroxidation decreased after surgical vagotomy and cholinergic blockade but increased after sensory deafferentation; (5) liver reduced glutathione decreased following vagotomy and sensory denervation in basal state and by cholinergic blockade in basal state and during endotoxemia; (6) nitric oxide increased by vagotomy in basal state and by sensory denervation and cholinergic blockade in basal state and during endotoxemia; (7) liver histological damage increased by subdiaphragmatic vagotomy, sensory denervation or cholinergic blockade. These findings suggest that: (1) sensory fibers (signals from the periphery) running in the vagus nerves are important in maintaining the redox status of the brain; (2) capsaicin vagal sensory nerves are likely to maintain nitric oxide tone in basal conditions; (3) the vagus nerve modulates liver redox status and nitric oxide release, (4) the vagus nerve mediates protective role in the liver with both cholinergic and capsaicin-sensitive mechanisms being involved.