Specific binding of 3H-tiotidine to histamine H2 receptors in guinea pig cerebral cortex

Although the H2 subclass of histamine receptor has been revealed by classical pharmacological approaches, the direct identification of this adenylate cyclase-linked receptor has, despite much effort, remained elusive. Initial studies using 3H-metiamide and 3H-histamine and, subsequently, work from our own laboratory and others using 3H-cimetidine and 3H-ranitidine in various tissues, has shown the unsuitability of these ligands for labelling the H2 receptor. We report here our results using 3H-tiotidine, a more potent H2-antagonist than either cimetidine or ranitidine, and show that this ligand meets the criteria for labeling the H2 receptor in guinea pig cerebral cortex membranes.