Characterization of neuronal and vascular histamine receptors mediating the salivary and vasodilator responses to histamine of the dog submandibular gland.

The submandibular gland in situ was perfused with blood through the glandular artery at constant pressure in anesthetized dogs, and all drugs were administered intra-arterially. During infusion of metiamide, histamine and 2-(2-pyridyl)ethylamine (PEA) produced salivary and vasodilator responses consisting of an early and a late component. The dose-response curves for respective components of the salivary and vasodilator responses to PEA were parallel with the corresponding curves for histamine and in producing these responses PEA was about 40 times less potent than histamine on a molar basis. During infusion of mepyramine, histamine and dimaprit produced only the early vasodilator response. The dose-vasodilator response curves to histamine and dimaprit were parallel, and dimaprit was about 750 times less potent than histamine on a molar basis. The present results support the conclusion obtained in a previous study that neuronal histamine receptors mediating the whole salivary and the late vasodilator response are exclusively of the H1-type and vascular histamine receptors mediating the early vasodilator response consist of both H1-and H2-type although the former is predominant.