Summary
The transient depolarizations inAcetabularia which fulfill the essential criteria of an action potential (all-or-none characteristics, triggering by depolarization, propagation, etc.) are investigated. These action potentials are analyzed by conductance measurements and voltage clamp experiments on the basis of the analog circuit of the membrane (Gradmann, D. 1975.J. Membrane Biol. 25:183). It is concluded that these action potentials do not arise by permeability changes of the passive diffusion channels, but by the active pathway of the electrogenic pump, which consists of a voltage sourceE P of about −200 mV in series with two nonlinear conducting elementsP1 andP2, the latter andE P being shunted by a large quasi capacityC P of some mF cm−2. The nonlinear current-voltage relationship of the carrier system (P1) is not changed during the action potential but has an effect on its time course. However, the elementsP2 andC P , which probably reflect metabolic entities, are suggested to control the action potentials.
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Gradmann, D. “Metabolic” action potentials inAcetabularia . J. Membrain Biol. 29, 23–45 (1976). https://doi.org/10.1007/BF01868950
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DOI: https://doi.org/10.1007/BF01868950