Permeability changes associated with prolonged action potentials have been analyzed in procaine-treated crayfish abdominal muscle fibers. The effect of external Ca indicates that the increase in membrane conductance observed during the rising phase of the action potential is primarily due to a permeability increase for Ca. A remnant of the permeability increase may cause the succeeding plateau as shown by its high conductance and by the effect of low Mn. A delayed increase in conductance precedes the termination of the plateau phase. This is due to a delayed increase in permeability, probably for K, that is observed when depolarizing electrogenesis is eliminated. High external Ca reduces the action potential duration, the falling phase starting at a higher depolarization. These changes may be related to an earlier onset of the delayed increase in permeability, induced by a larger inside positivity in the presence of higher Ca. No "anomalous rectification" is seen in early or late I-V curves for small depolarizations. Ba may replace Ca in its role in depolarizing electrogenesis, and the first action potential induced in Ba saline has a large overshoot and a long duration. In higher Ba salines, action potentials are greatly prolonged. Long term soaking in Rb-containing or K-free saline also augments and prolongs the action potential. These changes are assumed to be related to depression of the K permeability of the membrane.
Article| March 01 1967
Permeability Changes Associated with the Action Potential in Procaine-Treated Crayfish Abdominal Muscle Fibers
From the Laboratory of Neurophysiology, Department of Neurology, College of Physicians and Surgeons, Columbia University, New York, New York, and the Marine Biological Laboratory, Woods Hole, Massachusetts.
Dr. Takeda's present address is Department of Physiology, Faculty of Medicine, Kanazawa University, Kanazawa, Japan
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Kimihisa Takeda; Permeability Changes Associated with the Action Potential in Procaine-Treated Crayfish Abdominal Muscle Fibers . J Gen Physiol 1 March 1967; 50 (4): 1049–1074. doi: https://doi.org/10.1085/jgp.50.4.1049
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