This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General physiology, Subject name: Physiology
Neurotransmitter for pain is 
Select and explain. 
A. Dopamine, B. Substance P, C. PAF, D. None
B: Substance P
Answer: B: Substance P 
Explanation: Substance P a polypeptide neurotransmitter that stimulates vasodilation and contraction of intestinal and other smooth muscles. It also plays a pa in salivary secretion, diuresis, natriuresis, and pain sensation. It has been isolated from ceain cells of the GI and biliary tracts.Ref: Ganong&;s review of medical physiology 23rd edition Page no: 143