The effect of atropine and metiamide on pepsin secretion of the rat.

The inhibition of pepsin secretion by metiamide and atropine was studied by perfusing the stomach lumen of anaesthetized rats. Atropine was more effective than metiamide in the inhibition of pepsin secretion induced by pentagastrin or carbachol. Perfusion of the stomach with a weak acid solution stimulated pepsin secretion, which was only abolished by atropine. Metiamide was ineffective. It is postulated that (1) hydrogen ions probably stimulate pepsin secretion, (2) a cholinergic-like reflex may be involved in this stimulation, (3) anticholinergics are direct and strong inhibitors of pepsin secretion, (4) histamine H2-receptor antagonists probably inhibit pepsin secretion indirectly via reduction of acid output.