Are histamine receptors involved in the stimulant activities of thiazolylethylamines supposed as cyclic models of dimaprit?

A representative group of 2-aminothiazolylethylamine derivatives, in which the gastric acid secretion stimulating S-aminoalkylisothiourea moiety can be recognized, was tested. The quite different responses observed suggest that in vivo but not in vitro some events mimicking an H2-receptor agonist-like activity rather than a direct interaction with H2-receptors could take place. On the basis of structure-activity relationships, it can be speculated that the active conformation of dimaprit is not that resembled by these compounds which have been considered as cyclic models of one of its possible conformations.