This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Autonomic nervous system, Subject name: Pharmacology
Methacholine has maximum agonist action at which of the following cholinergic receptors? 
Select and explain. 
A. M1, B. M2, C. M3, D. M4
B: M2
Answer: B: M2 
Explanation: Methacholine is a non selective muscarinic agonist. It has maximum agonist action on M2 receptor Relative Lee selective agonist of cholinergic receptor are: M1 selective: Oxotremorine M2 selective:metha methach ME selective: bethanechol Ref- katzung 12/e p100; KDT 7/e p101