N, N-Dimethyl-N'-[2-(diisopropylamino) ethyl]-N'-(4, 6-dimethyl-2-pyridyl) urea (8g) was the most potent example of the class. Comparison of this compound with cimetidine showed it to be equipotent in dogs stimulated with gastrin tetrapeptide but approximately half as potent in dogs stimulated with histamine. Inhibition of secretion does not appear to result from antagonism of the histamine Hz receptor, since the compounds show only weak inhibition ...