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
[{'content': 'Which of the following substance causes retrograde contraction during gut peristalsis? \nSelect and explain. \nA. NO, B. Vasoactive Intestinal peptide, C. Substance P, D. None of the above', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Retrograde contraction by\nAnterograde relaxation by\n\n\n\nAcetycholine\nSubstance P\nSerotonin\n\n\nNO\nVasoactive Intestinal Peptide', 'role': 'assistant'}]