Dopamine-1 receptor stimulation attenuates the vasoconstrictive response to gut ischemia

The effects of fenoldopam, a dopamine-1 (DA-1) receptor agonist, were studi ed in two groups of anesthetized dogs before and after inducion of splanchn ic ischemia by way of hemorrhage. During the first portion of the experimen t, both groups received fenoldopam (1.5 mug.kg (-1).min(-1)) for 45 min fol lowed by a 45-min washout. During the second portion, hemorrhage (10 ml/kg) was induced, followed by no intervention in group I (controls) and restart ing of the fenoldopam infusion in group II. Prehemorrhage, fenoldopam incre ased composite portal blood flow by 33% (P < 0.01). After hemorrhage-induce d splanchnic ischemia, fenoldopam restored portal vein blood flow to near b aseline, maintained the splanchnic fraction of cardiac output, and attenuat ed the rise in gut mucosal PCO2. DA-1 receptor stimulation increased portal blood flow and redistributed blood flow away from the serosal layer in fav or of the mucosa during basal conditions and after hemorrhage, suggesting a more concentrated distribution of splanchnic DA-1 receptors within the muc osal layer vasculature. Fenoldopam maintained splanchnic blood flow during hypoperfusion and attenuated the splanchnic vasoconstrictive response to he morrhage.