There are five muscarinic receptor subtypes expressed in the human heart. The main subtype is the M2-muscarinic receptor. We hypothesized that overexpression of the M2-muscarinic receptor should augment any contractile effects that are M2-muscarinic receptor-mediated. Therefore, we generated a transgenic mouse with overexpression of the human M2-muscarinic receptor under the control of the heart-specific α-myosin heavy chain promoter (M2-TG). We performed contraction experiments with electrically stimulated (1 Hz) left atrial preparations (LA) and spontaneously beating right atrial preparations (RA) from adult M2-TG or from adult wild-type littermate mice (WT). We confirmed the expression of the human M2-muscarinic receptor in the mouse heart by reverse transcription polymerase chain reaction (RT-PCR) and radioligand binding experiments at cardiac membranes and tissue sections. We did not detect differences in hematoxylin/eosin staining or Masson/Goldner staining between M2-TG and WT. We noticed that carbachol (10 nM-10 µM cumulatively applied) alone or in the presence of 1 µM isoprenaline reduced the force of contraction (FOC) to a similar extent in LA from M2-TG and WT. The beating rate in RA was similarly decreased by carbachol alone or by carbachol in the presence of 1 µM isoprenaline in M2-TG and WT. Overall, the number of RA that displayed absolute arrhythmias was higher in atria from M2-TG compared to atria from WT. No arrhythmias were noted in LA from M2-TG or WT. Stimulation of human M2-muscarinic receptors induced absolute atrial arrhythmias more often in RA from M2-TG than in RA from WT. Overexpressed M2-muscarinic receptors were silent to the force and beating rate.

• Klíčová slova
• Arrhythmia, Human M2-muscarinic receptors,
• Publikační typ
• časopisecké články MeSH

Muscarinic acetylcholine receptors are metabotropic G-protein coupled receptors. Muscarinic receptors in the cardiovascular system play a central role in its regulation. Particularly M2 receptors slow down the heart rate by reducing the impulse conductivity through the atrioventricular node. In general, activation of muscarinic receptors has sedative effects on the cardiovascular system, including vasodilation, negative chronotropic and inotropic effects on the heart, and cardioprotective effects, including antifibrillatory effects. First, we review the signaling of individual subtypes of muscarinic receptors and their involvement in the physiology and pathology of the cardiovascular system. Then we review age and disease-related changes in signaling via muscarinic receptors in the cardiovascular system. Finally, we review molecular mechanisms involved in cardioprotection mediated by muscarinic receptors leading to negative chronotropic and inotropic and antifibrillatory effects on heart and vasodilation, like activation of acetylcholine-gated inward-rectifier K+-currents and endothelium-dependent and -independent vasodilation. We relate this knowledge with well-established cardioprotective treatments by vagal stimulation and muscarinic agonists. It is well known that estrogen exerts cardioprotective effects against atherosclerosis and ischemia-reperfusion injury. Recently, some sex hormones and neurosteroids have been shown to allosterically modulate muscarinic receptors. Thus, we outline possible treatment by steroid-based positive allosteric modulators of acetylcholine as a novel pharmacotherapeutic tactic. Keywords: Muscarinic receptors, Muscarinic agonists, Allosteric modulation, Cardiovascular system, Cardioprotection, Steroids.

• MeSH
• agonisté muskarinových receptorů farmakologie   MeSH
• kardiotonika farmakologie   terapeutické užití   MeSH
• lidé MeSH
• receptory muskarinové * metabolismus   MeSH
• vazodilatace fyziologie   účinky léků   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH
• Názvy látek
• agonisté muskarinových receptorů MeSH
• kardiotonika MeSH
• receptory muskarinové * MeSH