Pharmacology Cardiovascular system ea1dea4b Activation of postsynaptic M2 receptors on the hea is associated with A Activation of adenylyl cyclase B Opening of Na+/K+ cation channels C Decrease in cAMP formation D Increase in IP3 and DAG High-Yield Explanation M2 and M4 receptors act by the opening of K+ channels. M1 and M4 act by the IP3-DAG pathway.