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α1-Adrenoceptor Blockade by Class I Antiarrhythmic Drugs in Guinea Pig Thoracic Aorta as Revealed by Mechanical and

Iyuki Namekata1, Maika Seki1, Hiro Igarashi1

  • 1Department of Pharmacology, Faculty of Pharmaceutical Sciences, Toho University, 2-2-1 Miyama, Funabashi, Chiba 274-8510, Japan.

Biological & Pharmaceutical Bulletin
|February 24, 2025
PubMed

Insights

Certain class I antiarrhythmic drugs, including cibenzoline and quinidine, exhibit alpha1-adrenoceptor blocking activity. This action was observed in guinea pig thoracic aorta tissue at therapeutically relevant concentrations.

Area of Science:

  • Pharmacology
  • Cardiovascular Research
  • Adrenergic Receptor Signaling

Background:

  • Alpha1-adrenergic receptors regulate vascular smooth muscle contraction.
  • Class I antiarrhythmic drugs are used to treat cardiac arrhythmias.
  • Potential off-target effects of antiarrhythmic drugs on vascular receptors warrant investigation.

Purpose of the Study:

  • To investigate the alpha1-adrenoceptor blocking activity of thirteen Vaughn Williams class I antiarrhythmic drugs.
  • To determine if these drugs affect phenylephrine-induced contraction in guinea pig thoracic aorta.
  • To assess the therapeutic relevance of any observed alpha1-adrenoceptor blockade.

Main Methods:

  • Isolated guinea pig thoracic aorta tissue preparations were used.
  • Phenylephrine and prostaglandin F2α were used to induce contractions.
  • Drug effects on contraction and smooth muscle staining with fluorescent prazosin were measured.
  • pA2 values were determined to quantify receptor antagonism.

Main Results:

  • Cibenzoline, quinidine, aprindine, ranolazine, and prazosin inhibited phenylephrine-induced contraction and reduced fluorescent prazosin staining.
  • Propafenone showed similar effects but also inhibited prostaglandin F2α-induced contraction.
  • Disopyramide, pirmenol, procainamide, lidocaine, mexiletine, flecainide, pilsicainide, and GS-458967 had no significant effect.
  • Observed effects for some drugs were at therapeutically relevant concentrations.

Conclusions:

  • Cibenzoline, aprindine, propafenone, quinidine, and ranolazine possess alpha1-adrenoceptor blocking activity.
  • This activity may contribute to their overall pharmacological profile.
  • The findings highlight potential vascular effects of specific class I antiarrhythmic drugs.

Keywords:
blockadeclass I antiarrhythmic drugα-adrenoceptor

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