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<p>There are five muscarinic receptor subtypes expressed in the human heart. The main subtype is the M<sub>2</sub>-muscarinic receptor. We hypothesized that overexpression of the M<sub>2</sub>-muscarinic receptor should augment any contractile effects that are M<sub>2</sub>-muscarinic receptor–mediated. Therefore, we generated a transgenic mouse with overexpression of the human M<sub>2</sub>-muscarinic receptor under the control of the heart-specific α-myosin heavy chain promoter (M<sub>2</sub>-TG). We performed contraction experiments with electrically stimulated (1&#xa0;Hz) left atrial preparations (LA) and spontaneously beating right atrial preparations (RA) from adult M<sub>2</sub>-TG or from adult wild-type littermate mice (WT). We confirmed the expression of the human M<sub>2</sub>-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 M<sub>2</sub>-TG and WT. We noticed that carbachol (10&#xa0;nM–10&#xa0;µM cumulatively applied) alone or in the presence of 1&#xa0;µM isoprenaline reduced the force of contraction (FOC) to a similar extent in LA from M<sub>2</sub>-TG and WT. The beating rate in RA was similarly decreased by carbachol alone or by carbachol in the presence of 1&#xa0;µM isoprenaline in M<sub>2</sub>-TG and WT. Overall, the number of RA that displayed absolute arrhythmias was higher in atria from M<sub>2</sub>-TG compared to atria from WT. No arrhythmias were noted in LA from M<sub>2</sub>-TG or WT. Stimulation of human M<sub>2</sub>-muscarinic receptors induced absolute atrial arrhythmias more often in RA from M<sub>2</sub>-TG than in RA from WT. Overexpressed M<sub>2</sub>-muscarinic receptors were silent to the force and beating rate.</p>

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Initial characterization of M2-muscarinic receptor overexpressing mouse heart

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年8月13日

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  • Ulrich Gergs,
  • Igor B. Buchwalow,
  • Britt Hofmann,
  • Jaromir Myslivecek,
  • Katerina Janisova,
  • Katarina Hadova,
  • Franziska Schettler,
  • Max Keller,
  • Jan Klimas,
  • Joachim Neumann

摘要

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.