Role of dopamine receptors and the utility of dopamine agonists in heart failure.

The existence of two dopamine receptor subtypes (DA1 and DA2) has been firmly established. Activation of DA1 receptors is associated with vasodilation, primarily in the renal, mesenteric, cerebral, and coronary arterial beds, and a natriuresis. DA2 receptors located on postganglionic sympathetic nerves and sympathetic ganglia mediate a decrease in the release of norepinephrine from sympathetic nerve terminals. The DA receptor activity of dopamine (which activates beta 1- and alpha-adrenoceptors as well as DA receptors) plays a prominent role in determining the beneficial hemodynamic responses to this drug in patients with heart failure. As a result, recent research efforts have been directed toward the development of dopamine analogues, which are orally effective and exhibit more selective agonist activity at DA receptors. Limited clinical experience in heart failure is now available for analogues with different spectra of receptor activity than dopamine, including selective DA1 and DA2 agonists. A review of these data is presented with an attempt to define the clinical relevance of the DA receptor-agonist properties of the compounds. Although the results of early clinical studies with some of these first-generation dopamine congeners are encouraging, analysis of ongoing large-scale placebo-controlled trials will provide valuable insight into their utility as therapeutic agents for patients with heart failure.