Imidazoline derivatives and agmatine induce histamine release from the rat stomach.

Strips from rat glandular stomach were used to investigate whether the imidazoline derivatives clonidine, tolazoline and BDF 6143 (4-chloro-2(2-imidazolin-2-ylamino)-isoindoline) and the guanidine derivative agmatine are able to release histamine from histamine-storing cells. Histamine was detected and quantified by HPLC. Clonidine, tolazoline and agmatine concentration-dependently induced a release of histamine from the gastric strips, whereas BDF 6143 was ineffective. However, BDF 6143 abolished the release-inducing effect of clonidine and agmatine. It is concluded that imidazoline and guanidine derivatives can induce histamine release from histamine-storing cells in the stomach by a specific mechanism (possibly via imidazoline receptors) which in turn might lead to a relevant increase in gastric acid secretion.