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 mechanism of muscarinic acetylcholine receptor ● To describe the nature of atropine drug ● To describe the mechanism of atropine on the smooth muscle of the airway

3. Muscarinic Acetylcholine receptor M3: ● Also known as cholinergic receptor ● Encoded by human gene CHRM3 ● A G-protein which upregulates metaphosphate C and IP3 (inositol triphosphate) and intracelllar calcium as signaling pathway

4. Effects of Muscarinic Acetylcholine receptor M3 on the Smooth Muscles: ● As a GPCR (G-protein coupled receptor) and also causes an increase in intracellular calcium, it causes constriction of the smooth muscles of the airway (bronchoconstriction) ● However, activation of M3 increases the synthesis of nitric oxide that cause the relaxation of adjacent vascular smooth muscle cells which leads to vasodilation

5. ATROPINE ● A tropane alkaloid (nitrogenous, bicyclic organic compound) ● Extracted from: deadly nigthshade (Atropa belladona), jimsonweed ( Datura stramonium), mandrake (Mandragora officinarum) and other plants of Solanaceae (a family of flowering plants both agricultural and toxic plants) ● A competitive antagonist for the muscarinic acetylcholine receptor ● Classified as anticholinergic drug

6. Physiological Effects of Atropine: ● As a competitive antagonist of muscarinic acetylcholine receptors, it lowers the parasympathetic activity of muscles and glands ● Causes bronchodilation – since atropine has the ability to block the bronchoconstrictive effects of histamine, bradykinin, and eicosanoids ● Reduction of the mucus secretion and mucociliary clearance results to mucus plugs which may be an undesirable effect of atropine in patients with airway disease.

8. References: ● Katzung B.G. Basic and Clinical Pharmacolgy. 10 th edition. McGraw- Hill-Lange.Asia.2007. P113 ● Brunton, et. Al., Goodman and Gilman’s Manual of Pharmacology and Therapeutics.2008. McGraw-Hill, Inc. USA p.121 ● http://www.med.howard.edu/pharmacology/handouts/CHOL- 2.SUM.htm http://www.med.howard.edu/pharmacology/handouts/CHOL- 2.SUM.htm ● http://www.wikipedia.com