Inhibitory actions of a local neural reflex on propulsive activity of the esophageal striated muscle portion in rats

The aim of the present study was to clarify functional roles of a local neural reflex in propulsive activity of the rat esophageal striated muscle. Firstly, we established a method for measuring the volume of fluid expelled from an isolated esophageal segment to evaluate propulsive activity. Electrical stimulation to vagus nerves induced propulsion of intraluminal solution in the esophageal segment. The vagally evoked propulsion was abolished in the presence of d-tubocurarine. Next, this quantitative method was applied to examine the functional roles of intrinsic nerves in the esophagus. Capsaicin, a stimulant of primary afferents, inhibited the vagally mediated propulsion. A nitric oxide synthase inhibitor or a selective tachykinin NK1 receptor antagonist significantly blocked the inhibitory effect of capsaicin. These findings suggest that the local neural reflex, which consists of tachykininergic and nitrergic neurons, might participate in modulation of propulsive activity in the striated muscle portion of the rat esophagus.