Abstract
1. The electrical and the mechanical activity of isolated frog muscle fibres have been simultaneously recorded in a physiological solution which allows the development of a large tubular sodium current. 2. Under such experimental conditions, fibres develop long-lasting action potentials and strong mechanical responses. 3. In voltage-clamp experiments a slow inward current is revealed for depolarizations higher than +20 mV from the resting potential. This current increases until +40 to +50 mV and then decreases to reverse near +90 mV. The amplitude of the mechanical response increases with the potential to reach an optimum value between +40 and +50 mV and then decreases to stabilize when the depolarization is near +90 mV. 4. In the presence of picrotoxin the slow inward current is reversibly inhibited and the tension-depolarization curve has an S-shape as found in normal physiological conditions. 5. The dependence of a part of the contraction upon the slow inward current is reinforced by the fact that in a 50% sodium solution the amplitude of the current and that of the contraction are reduced in the same proportion. 6. Detubulated fibres failed to generate such a sodium inward current. 7. When sodium ions are replaced by lithium ions a slow inward lithium current develops but it does not induce a mechanical response. 8. Tetracaine reversibly inhibits the current-dependent component of the contraction without affecting the potential-dependent one. 9. It is concluded that the contraction recorded in the present experimental conditions is the sum of two components: one is potential-dependent and the other depends on a sodium-induced calcium release mechanism.
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- Adrian R. H., Chandler W. K., Hodgkin A. L. Voltage clamp experiments in striated muscle fibres. J Physiol. 1970 Jul;208(3):607–644. doi: 10.1113/jphysiol.1970.sp009139. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Adrian R. H., Peachey L. D. Reconstruction of the action potential of frog sartorius muscle. J Physiol. 1973 Nov;235(1):103–131. doi: 10.1113/jphysiol.1973.sp010380. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Almers W., Best P. M. Effects of tetracaine on displacement currents and contraction of frog skeletal muscle. J Physiol. 1976 Nov;262(3):583–611. doi: 10.1113/jphysiol.1976.sp011611. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Almers W. Local anesthetics and excitation-contraction coupling in skeletal muscle. Effects on a Ca++-channel [proceedings]. Biophys J. 1977 Jun;18(3):355–357. doi: 10.1016/S0006-3495(77)85620-8. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Almers W. Some dielectric properties of muscle membrane and their possible importance for excitation-contraction coupling. Ann N Y Acad Sci. 1975 Dec 30;264:278–292. doi: 10.1111/j.1749-6632.1975.tb31489.x. [DOI] [PubMed] [Google Scholar]
- Bonvallet R., Ildefonse M., Rougier O. Physiologie animale. -Mise en évidence d'une libération intracellulaire de calcium induite par les ions sodium au niveau de trabécules auriculaires de Grenouille. C R Seances Acad Sci D. 1980 Oct 13;291(6):557–560. [PubMed] [Google Scholar]
- Caillé J., Ildefonse M., Rougier O. Existence of a sodium current in the tubular membrane of frog twitch muscle fibre; its possible role in the activation of contraction. Pflugers Arch. 1978 May 18;374(2):167–177. doi: 10.1007/BF00581298. [DOI] [PubMed] [Google Scholar]
- Duval A., Léoty C. Ionic currents in mammalian fast skeletal muscle. J Physiol. 1978 May;278:403–423. doi: 10.1113/jphysiol.1978.sp012312. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Eisenberg R. S., Howell J. N., Vaughan P. C. The maintenance of resting potentials in glycerol-treated muscle fibres. J Physiol. 1971 May;215(1):95–102. doi: 10.1113/jphysiol.1971.sp009459. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Endo M. Calcium release from the sarcoplasmic reticulum. Physiol Rev. 1977 Jan;57(1):71–108. doi: 10.1152/physrev.1977.57.1.71. [DOI] [PubMed] [Google Scholar]
- FALK G., FATT P. LINEAR ELECTRICAL PROPERTIES OF STRIATED MUSCLE FIBRES OBSERVED WITH INTRACELLULAR ELECTRODES. Proc R Soc Lond B Biol Sci. 1964 Apr 14;160:69–123. doi: 10.1098/rspb.1964.0030. [DOI] [PubMed] [Google Scholar]
- Gage P. W., Eisenberg R. S. Capacitance of the surface and transverse tubular membrane of frog sartorius muscle fibers. J Gen Physiol. 1969 Mar;53(3):265–278. doi: 10.1085/jgp.53.3.265. [DOI] [PMC free article] [PubMed] [Google Scholar]
- HODGKIN A. L., HOROWICZ P. Movements of Na and K in single muscle fibres. J Physiol. 1959 Mar 3;145(2):405–432. doi: 10.1113/jphysiol.1959.sp006150. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Hille B., Campbell D. T. An improved vaseline gap voltage clamp for skeletal muscle fibers. J Gen Physiol. 1976 Mar;67(3):265–293. doi: 10.1085/jgp.67.3.265. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Hodgkin A. L., Nakajima S. The effect of diameter on the electrical constants of frog skeletal muscle fibres. J Physiol. 1972 Feb;221(1):105–120. doi: 10.1113/jphysiol.1972.sp009742. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Horackova M., Vassort G. Calcium conductance in relation to contractility in frog myocardium. J Physiol. 1976 Aug;259(3):597–616. doi: 10.1113/jphysiol.1976.sp011485. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Ildefonse M., Rougier O. Voltage-clamp analysis of the early current in frog skeletal muscle fibre using the double sucrose-gap method. J Physiol. 1972 Apr;222(2):373–395. doi: 10.1113/jphysiol.1972.sp009803. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Lowe D. A., Richardson N. P., Taylor P., Donatsch P. Increasing intracellular sodium triggers calcium release from bound pools. Nature. 1976 Mar 25;260(5549):337–338. doi: 10.1038/260337a0. [DOI] [PubMed] [Google Scholar]
- Léoty C., Alix J. Some technical improvements for the voltage clamp with the double sucrose gap. Pflugers Arch. 1976 Sep 3;365(1):95–97. doi: 10.1007/BF00583633. [DOI] [PubMed] [Google Scholar]
- Léoty C., Raymond G. Mechanical activity and ionic currents in frog atrial trabeculae. Pflugers Arch. 1972;334(2):114–128. doi: 10.1007/BF00586785. [DOI] [PubMed] [Google Scholar]
- Mironneau J. Excitation-contraction coupling in voltage clamped uterine smooth muscle. J Physiol. 1973 Aug;233(1):127–141. doi: 10.1113/jphysiol.1973.sp010301. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Palmer R. F., Posey V. A. Ion effects on calcium accumulation by cardiac sarcoplasmic reticulum. J Gen Physiol. 1967 Sep;50(8):2085–2095. doi: 10.1085/jgp.50.8.2085. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Potreau D., Raymond G. Calcium-dependent electrical activity and contraction of voltage-clamped frog single muscle fibres. J Physiol. 1980 Oct;307:9–22. doi: 10.1113/jphysiol.1980.sp013420. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Potreau D., Raymond G. Slow inward barium current and contraction on frog single muscle fibres. J Physiol. 1980 Jun;303:91–109. doi: 10.1113/jphysiol.1980.sp013273. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Raymond G., Potreau D. Barium ions and excitation-contraction coupling of frog single muscle fibres under controlled current and voltage. J Physiol (Paris) 1977 Oct;73(5):617–631. [PubMed] [Google Scholar]
- Schneider M. F., Chandler W. K. Voltage dependent charge movement of skeletal muscle: a possible step in excitation-contraction coupling. Nature. 1973 Mar 23;242(5395):244–246. doi: 10.1038/242244a0. [DOI] [PubMed] [Google Scholar]
- Takeda K. Prolonged sarcotubular regenerative response in frog sartorius muscle. Jpn J Physiol. 1977;27(3):379–389. doi: 10.2170/jjphysiol.27.379. [DOI] [PubMed] [Google Scholar]
- Vassort G., Rougier O. Membrane potential and slow inward current dependence of frog cardiac mechanical activity. Pflugers Arch. 1972;331(3):191–203. doi: 10.1007/BF00589126. [DOI] [PubMed] [Google Scholar]
- Venosa R. A. Inward movement of sodium ions in resting and stimulated frog's sartorius muscle. J Physiol. 1974 Aug;241(1):155–173. doi: 10.1113/jphysiol.1974.sp010646. [DOI] [PMC free article] [PubMed] [Google Scholar]

