Computational model of rabbit SA node pacemaker activity probed with action potential and calcium transient clamp

Area of Science:

• Computational biology
• Cardiac electrophysiology
• Mathematical modeling

Background:

• Numerous computational models of sinoatrial (SA) nodal cell pacemaker activity exist, derived from patch-clamp data.
• These models exhibit significant discrepancies in quantifying the roles of individual ionic currents in diastolic depolarization and pacemaker function.
• Discrepancies may arise from variations in action potential shape and intracellular calcium transients between models, rather than inherent differences in ionic currents.

Purpose of the Study:

• To accurately determine the contribution of individual ionic currents to the pacemaker activity of SA nodal cells within a computational model.
• To address the limitations of existing models by accounting for realistic action potential shapes and calcium transients.

Main Methods:

• Simultaneously recorded membrane potential and intracellular calcium concentration ([Ca(2+)](i)) from isolated SA nodal myocytes.
• Applied an "action potential clamp" and "calcium transient clamp" to a computational model using experimental data.
• Used a data file containing experimentally recorded SA nodal action potentials and associated calcium transients to drive the model.

Main Results:

• Computed ionic currents that more closely represent the actual ionic currents during SA nodal myocyte pacemaker activity.
• Identified discrepancies between recorded and computed net membrane current, indicating potential model shortcomings.

Conclusions:

• The combined "action potential clamp" and "calcium transient clamp" method provides a more accurate assessment of ionic current contributions to SA nodal cell pacemaker activity.
• This approach helps to refine computational models by highlighting areas where model representations deviate from experimental data.