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: Physiology
Substance P, actions are all except 
Select and explain. 
A. Vasoconstriction, B. Pain transmission, C. Axon reflex, D. Peristalsis
A: Vasoconstriction
Answer: A: Vasoconstriction 
Explanation: Substance P saw at

Primary pain nerve endings in the dorsal horn of the spinal cord
Hypothalamus
Nigrostriatal pathway of basal ganglia

It is probably involved in pain transmission, axon reflex and peristalsis.