Action of dopamine in 1-2 mcg/kg/min dose is
**Core Concept**
The question tests the understanding of **dopamine**'s dose-dependent effects on the body, particularly its action on the **vascular bed** and **heart**. Dopamine is a **catecholamine** with varying effects based on the dosage used.
**Why the Correct Answer is Right**
At a dose of 1-2 mcg/kg/min, dopamine primarily stimulates **dopaminergic receptors**, leading to **vasodilation** in the **renal** and **mesenteric** blood vessels, increasing blood flow to these areas. This dose is often used to improve **renal perfusion** without causing significant **increases in heart rate** or **blood pressure**.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because at this dose, dopamine does not significantly increase heart rate or contractility.
**Option B:** Incorrect as this dose does not cause vasoconstriction.
**Option D:** Incorrect because it does not accurately describe the primary action at this dose range.
**Clinical Pearl / High-Yield Fact**
Remember, dopamine's effects are dose-dependent: low doses (1-2 mcg/kg/min) increase renal blood flow, moderate doses (2-10 mcg/kg/min) increase heart rate and contractility, and high doses (10-20 mcg/kg/min) cause vasoconstriction.
**Correct Answer:** B. Increases renal blood flow.