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Updated: Sep 30, 2026

Quantifying Agonist Activity at G Protein-coupled Receptors
Published on: December 26, 2011
Pharmacologic characterization of muscarine receptor subtypes in rat gastric fundus mediating contractile responses
D R Milovanović1, S M Janković
1Department of Pharmacology, Medical Faculty, University of Kragujevac, Serbia, Yugoslavia.
Abstract:
The role of four muscarinic receptor subtypes M1, M2, M3 and M4 which have been characterized pharmacologically was examined in motility control of isolated rat gastric fundus. Acetylcholine produced concentration-dependent tonic contraction of isolated rat fundus (EC50 = 9.64 +/- 0.14 x 10(-8)M). These contractions were concentration-dependently antagonized by atropine (KB = 2.45 x 10(-11)M), M1 selective blockers telenzepine (KB = 6.64 x 10(-11)M) and pirenzepine (KB = 2.3 x 10(-8)M), and hexocyclium (KB = 2.82 x 10(-10)M). M3-selective blocker p-fluoro-hexahydro-sila-difenidol (pFHHSiD) was a less potent antagonist (KB = 2.3 x 10(-8)M), while M2 and M4-selective methoctramine produced only weak blockade of tonic contractions caused by acetylcholine (KB = 4.68 x 10(-6)M). These results suggest that only M1 and M3 muscarinic receptors have functional roles in motility control of rat gastric fundus, M1 receptors being more important.
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