Hemodynamic and sympathetic effects of fenoldopam and sodium nitroprusside

Background: Fenoldopam is a novel dopamine‐1 receptor selective agonist that can be used as a vasodilator perioperatively to treat hypertension and to produce induced hypotension. We were interested to find out whether there were any differences between fenoldopam (FM) and sodium nitroprusside (SNP), one of the most popular vasodilators, in their effects on hemodynamics and sympathetic outflow using not only neuraxis intact but also baro‐denervated animal models. Methods: A total of 60 New Zealand white rabbits were divided into two groups of 30 each: the neuraxis‐intact group and the totally baro‐denervated group. Each group was further divided into three groups of 10 each to receive SNP 10 μg · kg−1, FM 10 μg · kg−1 or FM 20 μg · kg−1, respectively. Mean arterial pressure (MAP), heart rate (HR) and renal sympathetic nerve activity (RSNA) were recorded before and after intravenous (i.v.) administration of each agent. In addition, cardiac and sympathetic baroreflex sensitivity were assessed in the neuraxis‐intact animals. Results: In the neuraxis‐intact groups, although RSNA was increased to a similar extent in all three groups (P