Related Experiment Videos
Electrical effects of okadaic acid extracted from black sponge on rabbit sinus node
British Journal of Pharmacology
|October 1, 1990
Summary
Okadaic acid enhances spontaneous activity in rabbit sinus node pacemaker cells by increasing slow inward current. Its effects are dependent on sodium ions and sensitive to verapamil, suggesting a role for calcium channels.
Area of Science:
- Cardiovascular Physiology
- Cellular Electrophysiology
Background:
- The sinus node is the dominant pacemaker of the heart.
- Understanding factors influencing sinus node automaticity is crucial for cardiac rhythm regulation.
Purpose of the Study:
- To investigate the effects of okadaic acid on the electrical activity of rabbit sinus node pacemaker cells.
- To elucidate the ionic mechanisms underlying okadaic acid's influence on spontaneous firing.
Main Methods:
- Microelectrode techniques were employed to record electrical responses.
- Voltage-clamp experiments using a two-microelectrode technique were performed.
- Experiments were conducted in varying ionic conditions (low Ca2+, low Na+) and with verapamil.
Main Results:
- Okadaic acid (10-5 to 4x10-5 M) shortened the spontaneous action potential cycle length (SPCL).
- It increased maximum upstroke velocity (Vmax) and action potential amplitude.
- Effects were preserved in low Ca2+ but inhibited by low Na+ or verapamil.
- Okadaic acid increased slow inward current (Isi) in voltage-clamp studies.
Conclusions:
- Okadaic acid enhances sinus node pacemaker cell activity.
- This enhancement is mediated by an increase in verapamil-sensitive slow inward current (Isi).
- The findings highlight the role of calcium influx in regulating cardiac automaticity.