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Action potentials of the mollusk giant neuron with changes in extracellular concentrations of sodium and calcium ions


The action potential (AP) of the giant neuron of the molluskPlanorbis corneus exhibits an increased sensitivity of the spike overshoot to external sodium concentration in solutions containing a significantly lowered concentration of calcium. These results suggest that during the AP both sodium and calcium ions may act as carriers of the inward-directed current. During repeated responses the role of calcium ions in AP generation increases while that of sodium decreases. A delay in repolarization can occasionally be observed at the beginning of the falling phase of the AP. This delay is considered to be a result of a decrease in efficiency of the repolarizing action of the outward potassium current due to competition from a current entering the cell at the time of the falling phase. Results suggest that the carrier of this inward current is calcium.

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Additional information

A. A. Bogomolets' Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 1, No. 1, pp. 109–117, July–August, 1969.

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Magura, I.S. Action potentials of the mollusk giant neuron with changes in extracellular concentrations of sodium and calcium ions. Neurophysiology 1, 85–91 (1969).

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  • Calcium
  • Potassium
  • Generation Increase
  • Sodium Concentration
  • Potassium Current