What is the mechanism of action of dopamine?

From the Guidelines

Dopamine's mechanism of action involves binding to various receptor subtypes, including dopaminergic and adrenergic receptors, leading to dose-dependent effects on the cardiovascular system, such as vasodilation, increased cardiac contractility, and vasoconstriction. At low doses (<2 mg/kg/min i.v.), dopamine acts on peripheral dopaminergic receptors, causing vasodilation in the renal, splanchnic, coronary, and cerebral vascular beds, which can improve renal blood flow, glomerular filtration rate, diuresis, and sodium excretion rate 1. Some key points about dopamine's mechanism of action include:

• At higher doses (>2 mg/kg/min i.v.), dopamine stimulates β-adrenergic receptors, increasing myocardial contractility and cardiac output 1
• At doses >5 mg/kg/min, dopamine acts on α-adrenergic receptors, increasing peripheral vascular resistance 1
• Dopamine's effects are dose-dependent, making it useful in treating certain types of shock, although other medications like norepinephrine may be preferred in certain cases. The most recent and highest quality study on this topic is from the European Heart Journal in 2005, which provides a comprehensive overview of dopamine's mechanism of action 1.

From the FDA Drug Label

Dopamine exhibits an inotropic action on the myocardium, resulting in increased cardiac output. It causes less increase in myocardial oxygen consumption than isoproterenol and the effect of dopamine usually is not associated with tachyarrhythmia The drug also has been reported to produce dilation of the renal vasculature which is accompanied by increases in glomerular filtration rate, renal blood flow and sodium excretion.

The mechanism of action of dopamine is through its inotropic effect on the myocardium, which increases cardiac output. It also causes dilation of the renal vasculature, leading to increases in glomerular filtration rate, renal blood flow, and sodium excretion 2. Additionally, dopamine has a direct inotropic effect on the myocardium, increasing cardiac output at low or moderate doses, and its effects on specific vascular beds result in increased resistance in peripheral beds and decreased resistance in mesenteric and renal vascular beds 2.

• Key effects:
  • Increased cardiac output
  • Dilation of renal vasculature
  • Increased glomerular filtration rate
  • Increased renal blood flow
  • Increased sodium excretion
  • Increased mesenteric blood flow
• Main mechanism: Inotropic effect on the myocardium.

From the Research

Dopamine Mechanism of Action

Dopamine is a biogenic amine that plays a crucial role in various physiological processes, including cardiovascular, renal, hormonal, and central nervous system regulation. The mechanism of action of dopamine involves the stimulation of alpha and beta adrenergic and dopaminergic receptors.

Dopamine Receptors

There are two main subtypes of dopamine receptors: dopamine 1 (DA1) and dopamine 2 (DA2) receptors.

• DA1 receptors are involved in vasodilation, especially in the renal, coronary, mesenteric, and cerebral vascular beds 3.
• DA2 receptors are located at the endings of postganglionic sympathetic nerves and, when activated, inhibit norepinephrine release 3.

Agonists and Antagonists

Several agonists and antagonists of dopamine receptors have been identified, including:

• DA1 receptor agonists: fenoldopam, piribedil, ibopamine, SKF 3893, and apomorphine (nonspecific) 4.
• DA2 receptor agonists: bromocriptine, pergolide, lisuride, quinpirole, and carmoxirole 4.
• DA1 receptor antagonists: SCH23390 and clozapine 4.
• DA2 receptor antagonists: metoclopramide, domperidone, sulpiride, and haloperidol 4.

Cardiovascular Effects

The cardiovascular effects of dopamine agonists are complex and involve the stimulation of dopamine vascular and neuronal receptors, as well as the production of norepinephrine and epinephrine 5.

• Dopamine agonists can decrease blood pressure by inhibiting sympathetic neuronal discharge of norepinephrine and stimulating dopamine vascular receptors 5.
• DA1 receptor agonists can reduce afterload by causing peripheral vasodilation and produce natriuresis and diuresis 6.
• DA2 receptor agonists can reduce afterload by decreasing the release of norepinephrine and reducing the levels of renin-angiotensin-aldosterone system 6.

Therapeutic Significance

Dopamine agonists have therapeutic significance in the treatment of various conditions, including:

• Parkinson's disease: DA2 receptor agonists, such as bromocriptine and pergolide, can act on DA2 receptors in the nigrostriatal system to improve motor function 4.
• Congestive heart failure: DA1 receptor agonists, such as fenoldopam, and DA2 receptor agonists, such as ibopamine, can reduce afterload and improve cardiac function 6.
• Hypertension: DA1 receptor agonists, such as fenoldopam, and DA2 receptor agonists, such as bromocriptine, can lower blood pressure in experimental animals and hypertensive patients 3.