Cyamemazine

Cyamemazine is a neuroleptic agent that contains the phenothiazine chromophore. Cyamemazine is often used as an anxiolytic. Cyamemazine is a potent 5-HT₃ (K_i of 12 nM), 5-HT_2A (K_i = 1.5 nM) and 5-HT_2C (K_i of 75 nM) receptors antagonist with antipsychotic activity^[1][2]. In Vitro: Cyamemazine exhibits a high affinity for dopamine receptors, which is consistent with its antipsychotic activity. The antagonist activity of Cyamemazine at muscarinic receptors is consistent with its affinity for M₁ (K_i = 13 nM), M₂ (K_i = 42 nM), M₃ (K_i = 321 nM), M₄ (K_i = 12 nM), and M₅ (K_i = 35 nM) receptors^[1]. In Vivo: Cyamemazine behaves as an antagonist at the 5-HT₃, 5-HT_2C, and 5-HT_2A receptors in 5-HT₃-dependent contraction of isolated guinea pig ileum and bradycardic responses in rats, in 5-HT_2C-dependent phospholipase C stimulation in the rat brain membrane, and in 5-HT_2A-dependent contraction of isolated rat aorta rings and isolated guinea pig trachea. Cyamemazine antagonizes 5-HT₃ and 5-HT_2C receptors and that this effect is partially involved in its therapeutic activity in anxiety disorders. Acute administration of low doses of Cyamemazine can reduces extracellular dopamine and metabolite concentrations in rat striatum^[1].