Cyclooxygenase inhibition in the dorsal vagal complex of the rat evokes increases in gastric motor function

To characterize the involvement of brainstem cyclooxygenase (COX) in the vagal control of gastric motor function, tolmetin, a reversible COX inhibitor, was applied to the surface of the dorsal medulla oblongata or microinjected into the dorsal vagal complex (DVC) in alpha-chloralose anesthetized rats, while intragastric pressure and contractile activity of the pyloric circular and greater curvature longitudinal muscle were monitored. Tolmetin, applied to the surface of the medulla oblongata, increased intragastric pressure and stimulated contractile activity of gastric smooth muscle. Comparable gastric motor effects were observed after microinjection of tolmetin into the DVC. All the effects of tolmetin were abolished by bilateral vagotomy at the midcervical level. These results demonstrate for the first time that COX inhibition evokes vagally-mediated gastric motor effects in the DVC of the rat and support a role for COX products in gastrointestinal regulation.