Histamine H1-receptor antagonist activity assessed in conscious dogs

A simple, minimally invasive technique is described which allows assessment of histamine H1-receptor antagonist activity in conscious dogs. The technique is based on the inhibition of the tachycardia caused by intravenous administration of the H1-receptor agonist, 2-pyridylethylamine. The response to 2-pyridylethylamine is dose dependent and is inhibited, in a dose-dependent manner by H1-receptor antagonists, such as temelastine, terfenadine, and chlorpheniramine. In contrast, cimetidine does not inhibit this response. This technique allows comparison of antagonist activity after either oral or intravenous administration of antagonists and also permits an assessment of the time course of antagonism.