This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Gastrointestinal System, Subject name: Physiology
[{'content': 'Antegrade peristalsis due to? \nSelect and explain. \nA. Ach, B. Serotonin, C. Substance P, D. VIP', 'role': 'user'}, {'content': 'Answer: A \nExplanation: - Excitatory neurotransmitters in ENS are Acetylcholine & substance P - Inhibitory neurotransmitters in enteric nervous system are NO & VIP - Acetylcholine is main excitatory neurotransmitter responsible for antegrade peristalsis', 'role': 'assistant'}]