1. Effect of Atropine on the Smooth Muscles of the Airway
Team 5: Abela, Caro, Cosalan, Dator, De Castro, Hernandez J, Hernandez L., Ishimura, Pascua, Que A.

2. Objectives: To describe the nature of atropine drug
To describe the mechanism of muscarinic acetylcholine receptor
To describe the mechanism of atropine on the smooth muscle of the airway

3. ATROPINE Muscarinic blocker
alkaloid
Extracted from deadly nigthshade Atropa belladona
Muscarinic blocker
competitive antagonist of muscarinic agonists (e.g. acetylcholine)

4. Muscarinic Acetylcholine receptor M3:
Also known as cholinergic receptor
Encoded by human gene CHRM3
G protein Coupled receptor
7 transmembrane (7-TM) or serpentine receptor
Found in smooth muscles and glands

5. Parasympathetic Nervous System
ligand
Phospholipase C
Ligand: acetylcholine (agonist)
Receptor: M3
Effector organ: smooth muscle and glands of the airway
Coupling protein: Gq protein
Effector or transducer: Phospholipase C

6. 2nd messengers: IP3 and DAG
Result: Calcium channels in ER and mitochondria open
Activation of PKC
Activation of CaM kinases
(Calcium/calmodulin dependent kinases)
Effect: smooth muscle contraction or bronchoconstriction
increased mucus secretion

8. Effect of Atropine Antagonist: atropine Effect: bronchodilation
decreased mucus secretion

9. Physiological Effects of Atropine:
Lowers the parasympathetic activity of muscles and glands
Causes bronchodilation
Reduction of mucus secretion
Undesirable effect: decrease in mucociliary clearance may dry the mucous membrane of the respiratory tract resulting in mucus plugs

11. References:
Katzung B.G. Basic and Clinical Pharmacolgy. 10th edition. McGraw-Hill-Lange.Asia P113
Brunton, et. Al., Goodman and Gilman’s Manual of Pharmacology and Therapeutics McGraw-Hill, Inc. USA p.121 g
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