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Junction potentials and action potentials of the crayfish myocardium
1Department of Physiology, Biophysics, and Neuro-Sciences, Centro de Investigacion y de Estudios Avanzados del IPN, Mexico City, Mexico.
Journal of Cardiovascular Electrophysiology
|January 1, 1996
Summary
Investigating crayfish hearts without the cardiac ganglion revealed that calcium currents drive action potential upstrokes. Junction potential decay and action potential repolarization are linked to neurotransmitter disappearance.
Area of Science:
- Neurophysiology
- Comparative Physiology
- Cardiovascular Physiology
Background:
- The crayfish cardiac ganglion modulates heart activity.
- Understanding myocardial electrophysiology requires isolating cellular components.
Purpose of the Study:
- To characterize junction and action potentials in crayfish myocardium.
- To investigate nerve stimulation effects without the cardiac ganglion.
Main Methods:
- Surgical removal of the cardiac ganglion in isolated crayfish hearts.
- Electrical stimulation of peripheral nerves.
- Pharmacological manipulation with tetrodotoxin, Cd2+, Ni2+, and tetraethylammonium.
Main Results:
- Isolated junction potentials and action potentials were recorded.
- Junction potentials showed amplitudes up to 25 mV with slow decay (time constant ~170 ms).
- Calcium channel blockers eliminated action potentials, while tetraethylammonium prolonged them.
Conclusions:
- Junction potential decay and late action potential repolarization may involve neurotransmitter disappearance.
- Action potential upstroke is mediated by calcium currents.
- Fast repolarization is likely due to the delayed rectifier current.