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
Activation of postsynaptic M2 receptors on the hea is associated with 
Select and explain. 
A. Activation of adenylyl cyclase, B. Opening of Na+/K+ cation channels, C. Decrease in cAMP formation, D. Increase in IP3 and DAG
B: Opening of Na+/K+ cation channels
Answer: B: Opening of Na+/K+ cation channels 
Explanation: M2 and M4 receptors act by the opening of K+ channels. M1 and M4 act by the IP3-DAG pathway.