In conscious dogs with gastric fistulae, Heidenhain pouches and Thomas duodenal fistulae, pentagastrin was found to be a more potent peak acid and pepsin stimulant in both innervated stomach and vagally denervated pouch than methacholine chloride. 2. Slopes of curves relating response to the logs of molar doses of pentagastrin and methacholine, at peak secretion, did not differ significantly. The maximal pentagastrin stimulated secretion from the pouch was smaller than that for methacholine; from the fistula they did not differ. 3. Ganglionic blockade depressed methacholine stimulated peak acid secretion, but did not affect pentagastrin stimulated acid secretion. Dose-response curves for methacholine-induced acid and pepsin secretion at the perigee did not differ from those obtained with ganglionic blockade. 4. Ganglionic blockade depressed pepsin secretion from the fistula whether stimulated with pentagastrin or methacholine. Pouch pepsin secretion was small and no difference between curves was seen.
