Effect of DA1 Receptor Blockade with SCH 23390 on the Renal Response to Electrical Stimulation of the Renal Nerves

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Abstract
To evaluate the existence of functional renal dopaminergic innervation in the dog, we studied the effects of direct electrical stimulation of the renal nerves (RNS) with and without blockade of the dopamine receptor (DA1) that mediates the vasodilating and natriuretic response to intrarenal infusin of DA. Before infusion of the DA1 receptor antagonist, SCH 23390, RNS at 1 Hz did not change renal blood flow (RBF) but caused decreased urinary sodium excretion (-53 .+-. 9%, P < 0.01) and fractional excretion of sodium (-47 .+-. 10%, P < 0.01). Stimulation at 4 and 12 Hz elicited marked renal vasoconstriction (.DELTA.RBF = -37 .+-. 12%, P < 0.05 and -57 .+-. 12%, P < 0.01, respectively). When RNS (1 Hz) was performed during DA1 receptor blockade with SCH 23390, 0.5 .mu.g .cntdot. kg-1 .cntdot. min-1 iv, the responses were not different than those before SCH 23390 infusion (urinary sodium excretion: -54 .+-. 7%, P < 0.01 and fractional excretion of sodium: -46 .+-. 5%, P < 0.01). Renal vasoconstriction was also not influenced by SCH 23390 (.DELTA.RBF = -35 .+-. 11%, P < 0.05 during 4 Hz RNS and -58 .+-. 12%, P < 0.01 at 12 Hz RNS). Thus, the present study does not support the concept of functional dopaminergic innervation of the canine kidney.