Effect of histamine and related compounds on gastric emptying of the conscious rat.

In conscious rats, histamine given intraperitoneally produced a delay in gastric emptying. A dose-dependent relationship was observed. The threshold dose was about 1 mg/kg, the calculated maximum dose 35 mg/kg. The inhibitory effect of histamine on gastric emptying was abolished by pretreatment with H1-receptor antagonists and mimicked by 2-aminoethylthiazole; on the contrary, an H2-receptor agonist (dimaprit) and H2 antagonists were completely ineffective. This suggested that receptors involved in delay of gastric emptying are of the H1 type. The inhibitory effect of histamine on gastric emptying was not modified by pretreatment with the well-known inhibitors of gastric secretion, metiamide and cimetidine. This is consistent with the idea that the delay in gastric emptying observed with histamine may not be related to the gastric properties of this compound.