Brain neurotransmitter receptor-binding characteristics in rats after oral administration of haloperidol, risperidone and olanzapine

Abstract

The present study was conducted to characterize the binding of neurotransmitter receptors (dopamine D 2, serotonin 5-HT 2, histamine H 1, adrenaline α 1 and muscarine M l receptors) in the rat's brain after the oral administration of haloperidol, risperidone, and olanzapine. Haloperidol at 1 and 3 mg/kg displayed significant activity to bind the D 2 receptor (increase in the Kd value for [ 3H]raclopride binding) in the corpus striatum with little change in the activity toward the 5-HT 2 receptor (binding parameters for [ 3H]ketanserin). In contrast, risperidone (0.1–3 mg/kg) showed roughly 30 times more affinity for the 5-HT 2 receptor than D 2 receptor. Also, olanzapine (1–10 mg/kg) was most active toward the H 1 receptor in the cerebral cortex, corpus striatum, and hippocampus, was less active in binding 5-HT 2 and D 2 receptors, and showed the least affinity for α 1 and M 1 receptors. In conclusion, haloperidol and risperidone administered orally selectively bind D 2 and 5-HT 2 receptors, respectively, in the rat brain, while olanzapine binds H 1, 5-HT 2, and D 2 receptors more than α 1 and M 1 receptors.