Dopamine-induced vasodilatation in the isolated perfused rat kidney

The administration of dopamine (5--100 microgram) in rat kidneys perfused with physiological solution containing vasopressin and pretreated with an alpha-adrenoreceptor antagonist produced dose-dependent vasodilatation. The dopamine receptor antagonist haloperidol produced marked dilatation in the preparation at high doses (10--50 microgram), while a low dose of haloperidol (5 microgram) had no significant effect on the response to dopamine. The response to dopamine, however, was significantly reduced by the dopamine receptor antagonist, ergometrine (50 microgram). This dose of ergometrine had no significant effect on the vasodilator response to acetylcholine (0.01--0.2 microgram) or glyceryl trinitrate (GTN, 0.05--1 microgram). Administration of the beta-adrenoreceptor antagonist propranolol (0.5 mg) had no significant effect on the response to dopamine.