[³H]mianserin: Differential labeling of serotonin₂ and histamine₁ receptors in rat brain

Mianserin, a tetracyclic antidepressant, is a potent serotinin (5-HT) and histamine H₁ antagonist in peripheral smooth muscle systems. Mianserin was found to possess high affinity for 5-HT₂ and histamine H₁ receptor binding sites in brain membranes. By using [³H]mianserin, both 5-HT₂ and histamine H₁ receptors can be specifically labeled in rat cerebra cortex membranes. Simultaneous incubation of brain membranes with 300 nM triprolidine or 30 nM spiroperidol enables the selective labeling of 5-HT₂ or histamine H₁ receptors, respectively. In the guinea-pig cerebellum, [³H]mianserin exclusively labels histamine H₁ receptors, since 5-HT₂ sites are virtually absent in this area.