This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiovascular system, Subject name: Pharmacology
[{'content': 'Activation of postsynaptic M2 receptors on the hea is associated with \nSelect and explain. \nA. Activation of adenylyl cyclase, B. Opening of Na+/K+ cation channels, C. Decrease in cAMP formation, D. Increase in IP3 and DAG', 'role': 'user'}, {'content': 'Answer: B \nExplanation: M2 and M4 receptors act by the opening of K+ channels. M1 and M4 act by the IP3-DAG pathway.', 'role': 'assistant'}]