Effect of intraduodenally administered histamine on gastric acid secretion in rats and guinea pigs.

We examined the effect of histamine administered intraduodenally as well as subcutaneously or intravenously on the gastric acid secretion in rats and guinea pigs, using a newly devised cannula. Intraduodenally administered histamine dihydrochloride caused a significant dose-dependent increase in the gastric acid secretion in rats. The maximal acid secretion, which corresponded to that after subcutaneous (20 mg/kg) or intravenous (10 mg/kg/hr) administration of histamine, was observed within 30 min after intraduodenal administration (40 mg/kg). The plasma concentrations of histamine determined 30 min after intraduodenal, subcutaneous, and intravenous administration of histamine were nearly the same. Pretreatment with aminoguanidine sulfate (diamine oxidase inhibitor) at 30 mg/kg significantly increased the gastric acid secretion caused by intraduodenal histamine. The gastric acid secretion stimulated by intraduodenal histamine was significantly inhibited by cimetidine, pirenzepine, and omeprazole, but remained unchanged with tripelennamine. Intraduodenal histamine (20 mg/kg) also maximally stimulated the gastric acid secretion in guinea pigs. The response was comparable to that with subcutaneous histamine (1 mg/kg). We conclude that intraduodenal histamine has the ability to stimulate gastric acid secretion in both rats and guinea pigs.