The spontaneous action potential of rabbit atrioventricular node cells

Area of Science:

• Cardiology
• Electrophysiology
• Cell Biology

Background:

• The rabbit atrioventricular (A-V) node is crucial for cardiac impulse conduction.
• Understanding the cellular mechanisms of A-V node automaticity is essential for diagnosing and treating arrhythmias.

Purpose of the Study:

• To investigate the electrophysiological properties of small, dissected rabbit A-V node specimens.
• To determine the contribution of intrinsic cellular properties to A-V node spontaneous activity.

Main Methods:

• Dissection of the rabbit A-V node into 15 small specimens (0.5 X 0.5 mm).
• Recording of spontaneous action potentials and membrane potentials.
• Assessment of excitability using ion channel blockers (TTX and is blockers).

Main Results:

• Most small A-V node specimens exhibited spontaneous action potentials with configurations similar to the intact node.
• Small specimens had a less negative resting membrane potential (-44 mV) compared to the intact node (-62 mV).
• Blockade of is channels rendered specimens inexcitable, while TTX had no significant effect.

Conclusions:

• The intrinsic properties of A-V node cells, particularly a low resting membrane potential, contribute to spontaneous action potential generation.
• Slow inward and outward currents are key mechanisms underlying A-V node automaticity, similar to the sinoatrial node.
• Dissected A-V node specimens retain functional automaticity, providing a model for studying cellular electrophysiology.