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Spontaneous mechanical activity in depolarized frog ventricle
The Journal of General Physiology
|August 1, 1976
Summary
Frog ventricle tissue can generate spontaneous contractions in a low sodium, low calcium, and high potassium solution. This activity is influenced by calcium levels and local anesthetics, suggesting intercellular communication without altered membrane potential.
Area of Science:
- Cardiovascular Physiology
- Cellular Electrophysiology
Background:
- Depolarized cardiac tissue can exhibit spontaneous mechanical activity.
- Ionic concentrations significantly influence cardiac muscle function.
Purpose of the Study:
- To investigate the conditions and mechanisms underlying spontaneous contractions in frog ventricle.
- To explore the role of extracellular ions and local anesthetics in cardiac excitability.
Main Methods:
- Depolarizing frog ventricle strips by altering bathing solution ionic composition (low Na+, low Ca++, high K+).
- Manipulating extracellular calcium and sodium concentrations.
- Assessing the effects of local anesthetics on spontaneous activity.
Main Results:
- Spontaneous contractions were induced in low Na+, low Ca++, high K+ solution.
- Activity was inhibited by prior calcium depletion and rapidly terminated by high Na+.
- Local anesthetics enhanced contractions in a dose-dependent manner.
- Contractions were relatively insensitive to extracellular [Ca++] and [Ca++]/[Na+]2 ratios.
Conclusions:
- Spontaneous mechanical activity in frog ventricle is dependent on specific ionic gradients.
- The observed rhythmic contractions suggest intercellular communication mechanisms independent of significant changes in membrane potential.