This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pharmacology
When a patient is already on atropine and i.v. administration of norepinephrine to him will lead to: 
Select and explain. 
A. Decrease in heart rate, B. Increase in heart rate, C. Decrease in pupil size, D. Decrease in peripheral resistance
A: Decrease in heart rate
Answer: A: Decrease in heart rate 
Explanation: None