The ability of the H3-receptor agonists and the pro-drug of α-methylhistamine to protect the rat gastric mucosa against damage by 0.6N HCl was evaluated.The histamine homolog impentamine, reported to display both partial agonist and antagonist properties, was also evaluated.The intragastric administration of (R)α-methylhistamine, its prodrug BP 2.94, and FUB 407 was shown to markedly reduce the formation of macroscopically evident gastric lesions produced by concentrated acid.Conversely, imetit, immepip and impentamine failed to modify the damaging effect of the concentrated acid.These results provide evidence that gastroprotection is selectively produced by (R)α-methylhistamine, its prodrug and FUB 407, but not by imetit and immepip.The latter compounds, classified as H3-receptor agonists, appear to discriminate between functional models, in that they express different pharmacol. behavior at H3-receptors present in central and peripheral systems to those receptors responsible for gastroprotection.