Accelerated communication H1 contractile and H2 relaxant receptors in canine gastric muscularis mucosae

Histamine had two effects on the contractility of canine gastric muscularis mucosae in vitro: relaxation at or below 10 microM and contraction at higher concentrations. Selective agonists and antagonists were used to test the possibility that these effects were mediated by different receptor subtypes. The H1-selective agonist 2-pyridylethylamine (2-PEA) and the H2-selective agonist dimaprit contracted and relaxed this muscle, respectively, …