This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Autonomic nervous system, Subject name: Pharmacology
A 33-year-old patient with septic shock is noted to have persistent hypotension despite IV dopamine infusion. The patient is treated with an IV infusion of epinephrine. With which adrenoceptor does epinephrine act to constrict vascular smooth muscle 
Select and explain. 
A. a1 -Adrenoceptors, B. a2 -Adrenoceptors, C. b1 -Adrenoceptors, D. b2 -Adrenoceptors
A: a1 -Adrenoceptors
Answer: A: a1 -Adrenoceptors 
Explanation: a1 -Adrenoceptors mediate vasoconstriction in many vascular beds. In skeletal muscle, epinephrine can act on b2 -adrenoceptors to cause vasodilation. Ref:- KD Tripathi