An ionic model for rhythmic activity in small clusters of embryonic chick ventricular cells

Area of Science:

• Cardiac Electrophysiology
• Computational Biology
• Developmental Biology

Background:

• Embryonic chick ventricular cells are a model for studying cardiac rhythm.
• Electrical activity in small cell clusters differs significantly from larger reaggregates.
• Understanding ionic mechanisms is crucial for cardiac function.

Purpose of the Study:

• To model the electrical activity of small clusters of embryonic chick ventricular cells.
• To investigate the roles of specific ionic currents (ICa, IKs, IKr, IK1) in spontaneous beating.
• To predict the effects of ion channel blockers on cardiac cell electrical activity.

Main Methods:

• Whole-cell patch-clamp recordings from 2-4 cell clusters.
• Application of ion channel blockers (D-600, diltiazem, almokalant, Ba2+).
• Development of a Hodgkin-Huxley-type ionic model incorporating multiple ion currents.

Main Results:

• The model accurately replicates spontaneous activity and responses to blockers.
• Calcium current (ICa) generates the slow upstroke; K+ currents (IKs, IKr, IK1) contribute to repolarization.
• Seal-leak current significantly influences diastolic depolarization and beat interval.

Conclusions:

• The developed ionic model provides a framework for understanding cardiac cell electrical behavior in small clusters.
• Simulations predict phenomena like annihilation and single-pulse triggering under partial ICa block.
• The model facilitates numerical investigation of cardiac rhythm dynamics, synchronization, and reentrant rhythms.