S-(+)-aporphines are not selective for human D3 dopamine receptors

Summary 1. Our aim was to test the hypothesis that selectivity for D₃ dopamine (DA) receptors may contribute to limbic anti-DA selectivity ofS-(+)-aporphine DA partial agonists.2. Affinity was tested with³H-emonapride, using human D₃ receptors in mouse fibroblasts and D₂ receptors in rat striatal tissue.3. D₃ receptors showed a picomolar affinity for³H-emonapride, Na⁺ dependence, and reversible saturability, as well as stereoselectivity. Confirmatory or novel D₃/D₂ pharmacologic selectivity was found with several benzamides, thioxanthenes, buspirone, GBR-12909, and DA agonists including hydroxyaminotetralins [ADTN, (+)-7-OH-DPAT, (–)-PPHT and its fluorescein derivative], (–)-N-propylnorapomorphine, (–)-3-PPP, (–)-quinpirole, and SDZ-205-502, but neither aminoergoline nor (+)-aporphine partial agonists.4. The results extend pharmacologic characterization of D₃-transfected cell membranes but fail to account for the high limbic anti-DA selectivity ofS-(+)-aporphines.