This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous (Pharmacology), Subject name: Pharmacology
Dopamine in dose concentration at <2mcg/kg/min acts predominantly on? 
Select and explain. 
A. Beta-1, B. D-1, C. Alpha-1, D. None
B: D-1
Answer: B: D-1 
Explanation: Ans. B. D-1At low doses (<=2mg/kg/minute)stimulates dopaminergic receptors on renal blood vessels leading to vasodilation. DA infusion at this rate may increase renal blood flow and promote diuresis.At intermediate infusion rates (2-5mg/kg/min), (used in CHF, cardiogenic shock)Stimulates b1 receptors on heart increasing cardiac contractility. Also stimulates D1 receptorsAt higher infusion rates (5-15mg/kg/min), (used for shock with oliguria)Acts on a1, leading to vasoconstriction and rise in BP. Also stimulates D1 & b1 receptors