This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Central Nervous system, Subject name: Pharmacology
A person taking tricyclic antidepressants presents with blurred vision and dry mouth. These adverse effects results due to blockade of: 
Select and explain. 
A. M3 muscarinic receptors, B. GABA receptor, C. H1 histamine receptors, D. 5HT2 receptors
A: M3 muscarinic receptors
Answer: A: M3 muscarinic receptors 
Explanation: Anticholinergic adverse effects of TCAs include dry mouth, constipation, blurring of vision, urinary retention, etc. REF:KD TRIPATHI 8TH ED.