Abstract
TheCl− and K+ currents underlying the action potential (AP) in the giant alga Chara were directly recorded with the action potential clamp method. An electrically triggered action potential was recorded and repetitively replayed as command voltage to the same cell under voltage clamp. The resulting clamp current was close to zero. Only the initial rectangular current used for stimulation was approximately reproduced by the clamp circuit. Inhibition of Cl− channels with niflumic acid or ethacrynic acid and of K+ channels with Ba2+ evoked characteristic compensation currents because the amplifier had to add the selectively inhibited currents. Integration of the compensation currents revealed a mean flux through Cl− and K+ channels of 3.3 10−6 and 2.1 10−6 mole M−2 AP−1 respectively. The dynamics of CI− and K+ channel activation/inactivation were obtained by converting the relevant clamp currents to ionic permeabilities using the Goldman-Hodgkin-Katz current equation. During the AP the Cl− permeability reaches a peak 370 ms, on average, after termination of the stimulating pulse. The following inactivation proceeds 3.6 times slower than the activation. The increase in K+ permeability lags behind the rise in Cl− permeability, reaching a peak approximately 2 s after the latter.
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Beilby MJ, Coster HGL (1979 a) The action potential in Chara corallina II. Two activation-inactivation transients in voltage clamps of the plasmalemma. Aust J Biol Sci 6:323–335
Beilby MJ, Coster HGL (1979 b) The action potential in Chara corallina III. The Hodgkin-Huxley parameters for the plasmalemma. Aust J Plant Physiol 6:337–353
Beilby MJ, Blatt MR (1986) Simultaneous measurements of cytoplasmic K+ concentration and plasma membrane electrical parameters in single membrane samples of Chara corallina. Plant Physiol 82:417–422
Blatt MR (1991) Ion channel gating in plants: physiological implications and integration for stomatal function. J Membrane Biol 124:95–112
Coleman HA (1986) Chloride currents in Chara — a patch clamp study. J Membrane Biol 93:55–61
De Haas V, Vogel W (1989) Sodium and potassium currents recorded during an action potential. Eur Biophys J 17:49–51
Doerr T, Denger R, Trautwein W (1989) Calcium currents in single SA nodal cells of the rabbit heart studied with action potential clamp. Pflügers Arch 413:599–603
Doerr T, Denger R, Doerr A, Trautwein W (1990) Ionic currents contributing to the action potential in single ventricular myocytes of the guinea pig studied with action potential clamp. Pflügers Arch 416:230–237
Findley G, Hope A (1964) Ionic relations of Chara australis. IX. Analysis of transient membrane currents. Aust J Biol Sci 17:400–411
Fischmeister R, DeFelice LJ, Ayer RK, Levi R, DeHaan RL (1984) Channel currents during spontaneous action potentials in embryonic chick heart cells. Biophys J 46:267–272
Frankenhaeuser B, Huxley AF (1964) The action potential in the myelinated nerve fibre of Xenopus laevis as computed on the basis of voltage clamp data. J Physiol (London) 171:302–315
Homann U, Thiel G (1994) Cl− and K+ channel currents during the action potential in Chara; simultaneous recording of membrane voltage and patch currents. J Membrane Biol 141:297–309
Hope AB, Walker NA (1975) The physiology of giant algal cells. Cambridge University Press, London
Ibarra J, Morley GE, Delmar M (1991) Dynamics of the inward rectifier K+ current during the action potential of guinea pig ventricular myocytes. Biophys J 60:1534–1539
Kikuyama M (1986) Ion effluxes during excitation of Characeae. Plant Cell Physiol 27:1213–1216
Lunevsky VZ, Zherelova OM, Vostrikov IY, Berestovsky GN (1983) Excitation of Characeae cell membranes as a result of activation of calcium and chloride channels. J Membrane Biol 72:43–58
Marten I, Zeilinger C, Redhead C, Landry DW, Al-Awqati Q, Hedrich R (1992) Identification and modulation of a voltage-dependent anion channel in the plasma membrane of guard cells by high-affinity ligands. EMBO J 11:3569–3575
Mazzanti M, DeFelice LJ (1987) Na channel kinetics during the spontaneous heart beat in embryonic chick ventricle cells. Biophys J 52:95–100
Miller AJ, Sanders D (1987) Depletion of cytosolic free calcium induced by photosynthesis. Nature 326:397–400
Okihara K, Kiyosawa K (1988) Ion composition of the Chara internode. Plant Cell Physiol 34:75–82
Shimmen T, Tazawa M (1983) Activation of K+-channel in membrane excitation of Nitella auxilliformis. Plant Cell Physiol 24:1511–1524
Tazawa M, Kishimoto U, Kikuyama M (1974) Potassium, sodium and chloride in the protoplasm of characeae. Plant Cell Physiol 15:103–110
Tester M (1988) Blockade of potassium channels in the lasmalemma of Chara corallina by tetraethylammonium, Ba2+, Na+ and Cs+. J Membrane Biol 105:77–85
Thiel G, Homann U, Gradmann D (1993) Microscopic elements of electrical excitation in Chara. Transient activity of Cl− channels in the plasma membrane. J Membrane Biol 134:53–66
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Thiel, G. Dynamics of chloride and potassium currents during the action potential in Chara studied with action potential clamp. Eur Biophys J 24, 85–92 (1995). https://doi.org/10.1007/BF00211403
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DOI: https://doi.org/10.1007/BF00211403