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[Effects of Cs on automaticity and pacemaker current If and Ik in rabbit sinus node cells]
1Department of Physiology, Shanghai Second Medical University, Shanghai 200025.
Sheng Li Xue Bao : [Acta Physiologica Sinica]
|April 28, 2001
Summary
Cesium (Cs) did not significantly alter rabbit sinoatrial node automatic discharge or diastolic depolarization. While blocking the If current, Cs did not affect Ik, suggesting If is not essential for initial SA node automaticity.
Area of Science:
- Cardiac Electrophysiology
- Ion Channel Physiology
- Sinus Node Function
Context:
- The sinoatrial (SA) node generates the heart's electrical impulse.
- Pacemaker mechanisms, particularly the ionic currents involved, are crucial for understanding cardiac rhythm.
- The role of the hyperpolarization-activated current (If) in SA node automaticity has been a subject of investigation.
Purpose:
- To investigate the role of the If current in the pacemaker mechanisms of rabbit SA node cells.
- To determine the effects of cesium (Cs), a known If blocker, on SA node automatic discharge and diastolic depolarization.
Summary:
- Conventional microelectrode and perforated patch clamp techniques were used on enzyme-isolated rabbit SA node cells.
- 2 mmol/L Cs showed minimal effect on SA node automatic discharge and the slope of diastolic depolarization.
- Cs blocked the If current and increased slope conductance but had little effect on the Ik current, suggesting If is not essential for the initial phase of rabbit SA node automatic activity.
Impact:
- Challenges the established view of If as the sole driver of pacemaking in the SA node.
- Provides new insights into the complex interplay of ionic currents governing cardiac automaticity.
- Informs future research on cardiac arrhythmias and potential therapeutic targets.