In vitro affinity (pKi) of various antipsychotic drugs for cloned dopamine D2 and D3 receptors (human and rat). None of the drugs shown here display >fourfold selectivity for D2 over D3 receptors. Data are from the National Institutes of Mental Health (NIMH) Psychoactive Drug Screening Program (PDSP) Ki database located at http://pdsp.cwru.edu/pdsp.asp and references therein. The number of individual values included in the average D2 and D3 affinities, respectively, are quetiapine 17, 10; remoxipride 8, 7; clozapine 33, 20; olanzapine 19, 12; loxapine 13, 4; ziprazidone 7, 5; risperidone 24, 13; chlorpromazine 19, 10; and haloperidol 39, 22. Radioligands used in determination of Ki values were [3H]-raclopride, [3H]-nemonapride, [125I]-iodosulpiride, [3H]-spiperone, or [3H]-N-methylspiperone.