Adrenergic receptors and gastric acid secretion in dogs. The influence of beta 2-receptors.

The action of adrenergic subtypes of receptors in gastric acid secretion is still uncertain. The purpose of this study was to establish the influence of beta 2-adrenoceptors in the regulation of gastric secretion in conscious gastric fistula dogs. A dose-related inhibitory effect of beta 2-adrenergic stimulation on gastric acid secretion was found. The rank order of this inhibition was: Pentagastrin greater than bethanechol greater than histamine stimulated acid output. The strong beta 2-adrenergic induced inhibition found for pentagastrin and bethanechol stimulated acid output followed the characteristics of a non-competitive mechanism, while the weaker inhibition of histamine induced acid output seemed to follow a competitive mechanism. The inhibitory effect was not mediated through a decreased gastrin release. Dopamine receptor blockade was found to be without any influence on the inhibitory effect of beta 2-adrenoceptors. It is concluded that beta 2-adrenoceptors inhibit gastric acid secretion through an effect on gastric mucosa. A working hypothesis involving an endogenous inhibitory substance is proposed.