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.

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

ATROPINE

● alkaloid● Extracted from deadly nigthshade Atropa

belladona● Muscarinic blocker ● competitive antagonist of muscarinic

agonists (e.g. acetylcholine)

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

Ligand: acetylcholine (agonist)Receptor: M3Effector organ: smooth muscle and glands of the airwayCoupling protein: Gq proteinEffector or transducer: Phospholipase C

Phospholipase C

Parasympathetic Nervous System

ligand

2nd messengers: IP3 and DAGResult: Calcium channels in ER and mitochondria open

Activation of PKCActivation of CaM kinases

(Calcium/calmodulin dependent kinases)Effect: smooth muscle contraction or bronchoconstriction

increased mucus secretion

Effect of Atropine

Antagonist: atropineEffect: bronchodilation

decreased mucus secretion

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

References:

● Katzung B.G. Basic and Clinical Pharmacolgy. 10th 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://m17mask.com/RedHandbook/006NerveAgents.htm

● http://nlp.postech.ac.kr/Research/POSBIOTM/image/GPCR/PLC.jpg

● http://www.wikipedia.com

● http://www.med.howard.edu/pharmacology/handouts/CHOL-2.SUM.htm