In anesthetized piglets the effect of intra-aortic infusion of an equimolar dose of serotonin and histamine, 25 nM/kg/min, on antral, duodenal, jejunal and ileal pressure was compared. Both amines resulted in a pressure increase in all segments; no significant difference in potency was observed.

The monoamines, 5-hydroxytryptamine (5-HT) or serotonin and histamine are present in the enterochromaffin cells and the neurons of the myenteric plexus of the gastrointestinal tract. Their actions are mediated by specific receptors and their subtypes: at least seven main classes for 5- HT and three for histamine (see e.g. 1; 2; 3, 4, 5). They also regulate their mutual release (6). To our knowledge no data are available on a comparison of the activity of both amines on gastrointestinal motility. Therefore, in the present study the influence of an equimolar dose of both amines on gastrointestinal pressure was studied in the anesthetized piglet.