Effect of two antiserotoninergic drugs, methysergide and metergoline, on gastric acid secretion and gastrin release in healthy man

The effects of acute oral administration of the antiserotoninergic drugs methysergide (3 mg) and metergoline (4 mg) on basal, submaximal (0.6 µg/kg i. m.) and maximal (6 µg/kg) pentagastrinstimulated gastric acid secretion, as well as on basal and food-induced gastrin release, have been evaluated in healthy volunteers. Methysergide significantly increased basal and submaximal pentagastrin-stimulated gastric acid secretion, and metergoline significantly inhibited gastric acidity in all experiments. Basal and stimulated serum gastrin concentrations were not modified by either drug. The effect of methysergide on gastric acid secretion was opposed to that of serotonin and was probably dependent on its antiserotoninergic action, but the decrease in gastric acidity caused by metergoline is not easily explained. Although the effect is similar to that of a dopamine infusion, it does not depend on dopamine receptor stimulation, since it was not influenced by pretreatment with metoclopramide. It is suggested that it might be due to the weak anticholinergic and/or antihistaminic properties of metergoline.