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Existence of functional M3-muscarinic receptors in the human heart

Pia Willmy-Matthes1, Kirsten Leineweber, Thekla Wangemann

  • 1Institute of Pharmacology, University of Halle, 06097 Halle, Germany.

Naunyn-Schmiedeberg'S Archives of Pharmacology
|October 2, 2003
PubMed

Insights

Functional M3 muscarinic receptors (M-receptors) in the human heart

Area of Science:

  • Cardiovascular Pharmacology
  • Receptor Pharmacology
  • Molecular Cardiology

Background:

  • Muscarinic receptors (M-receptors) are implicated in cardiac function.
  • Previous studies identified M3-subtype M-receptors mediating inositol phosphate (IP) formation in rat cardiomyocytes.

Purpose of the Study:

  • To identify the specific M-receptor subtype responsible for IP formation in the human heart.
  • To characterize the role of M-receptors in human atrial tissue.

Main Methods:

  • Human right atrial slices were labeled with [3H]-myo-inositol.
  • Carbachol was used to stimulate [3H]-IP formation.
  • The effects of various M-receptor antagonists (atropine, himbacine, pirenzepine, darifenacin) on carbachol-induced IP formation were assessed.

Main Results:

  • Carbachol significantly increased [3H]-IP formation in a dose-dependent manner.
  • Atropine completely blocked carbachol-induced IP formation.
  • The M3-selective antagonist darifenacin concentration-dependently inhibited IP formation, while himbacine and pirenzepine had minimal effects.

Conclusions:

  • Functional M3-subtype muscarinic receptors are present in the human right atrium.
  • These M3 receptors are coupled to inositol phosphate (IP) formation in human atrial tissue.

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