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': 'Mechanism of analgesia is by: \nSelect and explain. \nA. Nociceptin stimulation, B. Nocistatin stimulation, C. O.L.R.I, D. All', 'role': 'user'}, {'content': 'Answer: B \nExplanation: B i.e. Nocistatin stimulation', 'role': 'assistant'}]