The actions of dopamine and of sulpiride on regional blood flows in the rat kidney.

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Abstract
Blood flow was measured in the renal cortex and medulla of anesthetized rats by the H washout method. The effects of dopamine infusion were measured. Low doses of dopamine (20 and 65 nmol .cntdot. kg .cntdot. min) caused only small increases in renal blood flow, and a higher dose (200 nmol .cntdot. kg .cntdot. min) caused vasoconstriction. After .alpha.-blockade with phenoxybenzamine (9 .mu.mol/kg), all doses of dopamine caused vasodilatation in the cortex and medulla of the kidney. This dopamine-induced renal vasodilatation was abolished by sulpiride (0.7 .mu.mol/kg per min), but was only slightly attenuated by propranolol (10 .mu.mol/kg). Sulpiride did not significantly alter the renal blood flow responses to noradrenaline [norepinephrine, NA] or isoprenaline, or the blood pressure responses to histamine, acetylcholine, 5HT [serotonin], NA and isoprenaline. In normal rats, infusion of sulpiride generally caused a reduction in renal cortical blood flow. This response showed a positive correlation with the initial blood pressure. There may be specific dopamine receptors in the renal vasculature of the rat, and dopamine may play a role in the normal control of renal blood flow.