Increased histamine-output from the isolated gastric mucosa of the rat in response to pentagastrin and methacholine.

1 A rat isolated gastric mucosal preparation was used to monitor histamine output and acid secretion during stimulation by different secretagogues. 2 In non-stimulated preparations, spontaneous histamine output decreased over 450 min. 3 Stimulation of secretion with 4 (5)-methylhistamine or dibutyryl cyclic adenosine 3'5'-monophosphate (db cyclic AMP) and theophylline did not influence histamine output. 4 Pentagastrin, gastrin and methacholine increased both acid secretion and histamine output. Pentagastrin and gastrin mobilized six times more histamine and relation to acid secretion than did methacholine. 5 Spontaneous histamine output and secretagogue-induced increases were unaffected by changes in external Ca2+ (0.0 to 7.2 mM) or Mg2+ (1.2 to 4.8 mM). 6 These results support the hypothesis that mucosal histamine plays a more important role in the action of gastrin than of cholinomimetics on the parietal cell.