Histamine H₁ receptors identified in mammalian brain membranes with [³H]mepyramine

The antihistamine [³H]mepyramine binds to H₁ histamine receptors in mammalian brain membranes. Potencies of H₁ antihistamines at the binding sites correlate with their pharmacological antihistamine effects in the guinea pig ileum. Specific [³H]mepyramine binding is saturable with a dissociation constant of about 4 nM in both equilibrium and kinetic experiments and a density of 10 pmol per gram of whole brain. Some tricyclic antidepressants are potent inhibitors of specific [³H]mepyramine binding. Regional variations of [³H]mepyramine binding do not correlate with variations in endogeneous histamine and histidine decarboxylase activity.