Blockade of Dopamine Receptors in the Renal Vasculature by Isomers of Flupenthixol and Sulpiride

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Abstract
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) were studied. The vascular bed was contracted with prostaglandin F2.alpha. (10-7-3 .times. 10-6 M) and dose-dependently relaxed with dopamine. cis-Flupenthixol (10-9-10-7 M) antagonized competitively the response to dopamine (apparent pA2 [competitive antagonistic activity] = 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 l-sulpiride. 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.