Histidine decarboxylase inhibition by O-methyl-3(+)catechin and gastric acid secretion in the cat.

In the conscious cat the histidine decarboxylase inhibitor O-methyl-3(+)catechin (Zy 15029) promoted a dose-dependent atropine-sensitive increase in basal acid output. Gastric acid secretion stimulated by food or insulin at different time intervals after pretreatment with Zy 15029 was dose and time dependently diminished up to 70% whereas acid output following pentagastrin stimulation was not reduced by doses effective against the former two stimuli. Only a high dose, which due to side effects has to be claimed as not tolerable in the cat, reduced acid output by about 40%, when application of Zy 15029 and stimulation were 90 min apart. It is suggested that in the cat gastric acid response following the three different stimuli was at least in part but to a variable extent mediated by endogenous histamine. Dose-dependent side effects of Zy 15029 might have been due to histidine decarboxylase inhibition in brain and changes in histaminergic neurotransmission.