American Board of Surgery Qualifying Exam (ABS QE) Practice Test

What type of effect does dopamine have on beta receptors?

1. Increases blood pressure

2. Improves contractility and heart rate

3. Vasoconstriction

4. Decreases heart rate

The correct answer is: Improves contractility and heart rate

Dopamine interacts with beta-adrenergic receptors primarily through its action as an agonist. When dopamine stimulates beta-1 receptors in the heart, it leads to increased myocardial contractility and heart rate, which enhances cardiac output. This effect is crucial, particularly in situations requiring increased cardiac performance, such as heart failure or shock. While dopamine can affect peripheral vascular resistance through its action on alpha-adrenergic receptors at higher doses, its primary action at moderate doses significantly enhances contractility and heart rate via beta-1 receptor stimulation. It's important to note that the vasodilatory action of dopamine is mainly mediated through dopamine receptors and, to some extent, beta-2 receptors in vascular smooth muscle. Therefore, the choice highlighting improved contractility and increased heart rate correctly captures the physiological effects of dopamine on beta receptors.