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
[{'content': 'Neurotransmitter for pain is \nSelect and explain. \nA. Dopamine, B. Substance P, C. PAF, D. None', 'role': 'user'}, {'content': 'Answer: B \nExplanation: 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', 'role': 'assistant'}]