Peripheral dopamine receptor blockade by SCH 23390 and domperidone in vitro

The antagonist potencies of SCH 23390 and domperidone have been determined at vascular and neuronal dopamine receptors in the rabbit isolated splenic artery and rectococcygeus muscle, respectively. SCH 23390 was a potent, competitive antagonist at vascular (pA2 = 10.65) but not neuronal (pA2 less than 6.0) receptors. Domperidone was a potent, competitive antagonist at neuronal (pA2 = 7.9) but not vascular (pA2 less than 4.0) receptors. SCH 23390 and domperidone are, therefore, highly selective vascular and neuronal dopamine receptor antagonists respectively.