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Initial development of conduction pattern of spontaneous action potential in early embryonic precontractile chick
Insights
Early embryonic chick hearts show synchronized electrical activity. Conduction velocity slows at the heart
Area of Science:
- Developmental Biology
- Cardiovascular Physiology
- Electrophysiology
Background:
- Spontaneous action potential conduction is crucial for embryonic heart development.
- Understanding early cardiac electrical activity informs congenital heart defect research.
Purpose of the Study:
- To optically monitor and analyze the conduction velocity of spontaneous action potentials in developing chick hearts.
- To investigate the role of the primordial fusion line in cardiac electrical wave propagation during early embryogenesis.
Main Methods:
- Utilized a potential-sensitive merocyanine-rhodanine dye for optical monitoring of cardiac electrical activity.
- Simultaneously recorded spontaneous optical action signals from multiple regions of the embryonic chick heart (7-10 somite stages).
- Calculated conduction velocity based on signal delays between different cardiac regions.
Main Results:
- Spontaneous action potentials were nearly synchronized across different regions of the primitive heart.
- A significant slowing of the excitatory wave was observed at the primordial fusion line between the 7 and 9-somite stages.
- This conduction delay at the fusion line diminished by the late 9th to 10-somite stage.
Conclusions:
- Electrical coupling at the primordial fusion line is poor in early embryonic chick hearts (7-9 somites).
- Electrical coupling strengthens significantly by the late 9th or 10-somite stage, facilitating synchronized heart function.
- These findings provide insights into the developmental maturation of cardiac electrical conduction pathways.
Abstract:
The conduction of spontaneous action potentials in the 7-10 somite embryonic developing chick hearts was monitored optically using a potential-sensitive merocyanine-rhodanine dye. Spontaneous optical action signals from 5 to 12 different regions of the primitive heart were recorded simultaneously. Short delays were observed among firing times of the absorption signals which were nearly synchronized among the different regions. From these delays, we estimated the conduction velocity of the spontaneous excitatory waves. Usually, in the 7-somite to the beginning of the 9-somite stage, (i) excitatory waves conducted radially over one side of the prebeating heart, at a uniform rate; (ii) the "radially" spreading electrical wave slowed considerably within the primordial fusion line at the midline of the heart; and (iii) this delay disappeared in the later period of the 9-somite stage to the 10-somite stage. These observations suggest that electrical coupling among the cells within the primordial fusion line is poor during the 7 to 9-somite stage, and that the coupling is strengthened by the late 9th or 10th somite stage.