Abaperidone is a potent antagonist of 5-HT_2A receptor and dopamine D₂ receptor with IC₅₀s of 6.2 and 17 nM. IC50 & Target: IC50: 17 nM (D₂ receptor), 6.2 nM (5-HT_2A receptor)^[1] In Vitro: Abaperidone possesses good affinity for dopamine D₂ receptors, together with a greater affinity for 5-HT₂ receptors with IC₅₀ of 17 and 6.2 nM, reaspectively^[1]. In Vivo: The time course of the inhibition of climbing behavior for a period of several hours after oral administration of either 0.5 mg/kg of Abaperidone or risperidone is tested in mice. Also is included a comparative test of catalepsy induced by Abaperidone and risperidone along several hours following oral administration at several doses in rats. A somewhat lesser induction of catalepsy is observed for Abaperidone. A study of serum prolactin levels after oral administration of Abaperidone, haloperidol, and risperidone at 5 mg/kg for either 1 or 3 days in rats. Increases in prolactin levels after oral administration of Abaperidone are smaller than those for reference drugs^[1].