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We studied the renal vascular effects of flupenthixol and sulpiride isomers in the isolated perfused rat kidney in the presence of phenoxybenzamine (10(-5) M) and sotalol (10(-5) M). The vascular bed was contracted with prostaglandin F2 alpha (10(-7) -3 X 10(-6) M) and dose-dependently relaxed with dopamine. Cis-flupenthixol (10(-9)-10(-7) M) antagonized competitively the response to dopamine (apparent pA2 = 8.34 +/- 0.09; mean +/- SD) without affecting papaverine-induced relaxation. Trans-flupenthixol was without effect at 10(-7) M. The dopamine receptor antagonist activities of the sulpiride isomers are low and d-sulpiride is twice as active as 1-sulpiride. Thus, the renal vascular dopamine receptor can be further characterized by the relative antagonist activities of cis-flupenthixol and sulpiride and by a rather low stereospecificity in favor of d-sulpiride.