A patient with organophosphate poisoning is treated with atropine. Which muscarinic receptor subtype mediates the cardiac effects that atropine reverses in this setting?
- A M2 ✓
- B M1
- C M3
- D M4
Correct answer: A. M2
Explanation
Cardiac muscarinic receptors are of the M2 subtype, located in the SA node and AV node. Organophosphate poisoning causes excessive acetylcholine accumulation, activating M2 receptors to produce bradycardia and AV block. Atropine competitively blocks M2 receptors to reverse these effects. M1 is predominant in gastric glands and CNS; M3 mediates smooth muscle contraction and glandular secretion.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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