Figure 4.

Famotidine and cimetidine activity on histamine receptors. Experiments performed in duplicate. A. Competitive binding dose-response curves for famotidine and cimetidine on four histamine receptors with reference compounds. B. The partial agonist, famotidine, shows antagonist activity of H2 in the presence of potent endogenous agonist, histamine. C. Inverse agonism of famotidine and cimetidine on H2, whereas histamine stimulated cAMP production by 20-fold of basal (N=2). D. Arrestin recruitment by famotidine (left) and cimetidine (right) upon interaction with histamine receptors.