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Isolation of Human Atrial Myocytes for Simultaneous Measurements of Ca2+ Transients and Membrane Currents
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Electrophysiological effects of vasoactive intestinal peptide in rabbit atrium: a modulation of acetylcholine

F Halimi1, O Piot, L Guize

  • 1Department of Cardiology and INSERM U 256 Laboratory, Broussais Hospital, Paris, France.

Journal of Molecular and Cellular Cardiology
|January 1, 1997
PubMed

Insights

Vasoactive Intestinal Peptide (VIP) lengthens atrial action potential duration by activating calcium currents. VIP also modulates acetylcholine (Ach) effects, potentially controlling vagal atrial arrhythmias.

Area of Science:

  • Cardiovascular Physiology
  • Neuroendocrinology

Background:

  • Vasoactive Intestinal Peptide (VIP) is co-secreted with acetylcholine (Ach) in atrial tissue.
  • Understanding the electrophysiological roles of VIP and Ach is crucial for cardiac function.

Purpose of the Study:

  • To investigate the electrophysiological effects of VIP and Ach on rabbit isolated right atrium.
  • To elucidate the mechanism of VIP-induced action potential duration lengthening.
  • To determine the interaction between VIP and Ach in modulating atrial electrophysiology.

Main Methods:

  • Microelectrode technique used on isolated rabbit right atrium.
  • Superfusion with varying concentrations of VIP and Ach.
  • Experiments involving verapamil pretreatment to assess calcium current involvement.
  • Simultaneous perfusion of VIP and Ach to study their combined effects.

Main Results:

  • VIP significantly lengthened action potential duration at 90% repolarization (APD90) in a dose-dependent manner.
  • VIP-induced APD90 lengthening was abolished by verapamil, indicating calcium current activation.
  • Ach decreased APD90, while VIP counteracted this shortening effect when co-administered.
  • VIP lengthened effective refractory periods (ERP), whereas Ach decreased ERP.

Conclusions:

  • VIP lengthens atrial APD90, likely through calcium current activation.
  • VIP can modulate Ach activity, potentially mitigating Ach-induced APD90 shortening.
  • VIP's opposing effects on atrial ERP compared to Ach suggest a role in controlling vagal atrial arrhythmias.

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