Mediator release from isolated rat ileum in response to field stimulation

The effect of electrical field stimulation on mediator release from the isolated rat ileum was evaluated by recording the muscle responses and by measuring acetylcholine and histamine appearing in the perfusation fluid. In the presence of cholinesterase inhibitors, supramaximal field stimulation (10 Hz) resulted in twitch responses accompanied by an increased release of acetylcholine. The resting output of histamine was measurable also in the absence of inhibition of cholinesterases, and neatly increased during electrical stimulation. Atropine produced a dose-related decrease in the release of histamine from electrically stimulated muscle, while eserine extends the time-course of the contractile response and of the histamine release as well. The results are discussed in the context of the role ascribed to acetylcholine as a physiological modulator of histamine release.