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Sodium-dependent plateau potentials in electrocytes of the electric fish Gymnotus carapo

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Abstract

The weakly electric fish Gymnotus carapo emits a triphasic electric organ discharge generated by muscle-derived electrocytes, which is modified by environmental and physiological factors. Two electrode current clamp recordings in an in vitro preparation showed that Gymnotus electrocytes fired repetitively and responded with plateau potentials when depolarized. This electrophysiological behavior has never been observed in electrocytes from related species. Two types of plateaus with different thresholds and amplitudes were evoked by depolarization when Na+-dependent currents were isolated in a K+- and Ca2+-free solution containing TEA and 4-AP. Two electrode voltage clamp recordings revealed a classical fast activating–inactivating Na+ current and two persistent Na+-dependent currents with voltage-dependencies consistent with the action potential (AP) and the two plateaus observed under current clamp, respectively. The three currents, the APs and the plateaus were reduced by TTX, and were absent in Na+-free solution. The different Na+-dependent currents in Gymnotus electrocytes may be targets for the modifications of the electric organ discharge mediated by environmental and physiological factors.

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Fig. 1A–D
Fig. 2A–F
Fig. 3A–D
Fig. 4
Fig. 5A–C
Fig. 6A–E

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Abbreviations

4-AP:

4-Aminopyridine

AP:

Action potential

EO:

Electric organ

EOD:

Electric organ discharge

I-V/V-I:

Current–voltage/voltage–current

MP:

Membrane potential

PSP:

Postsynaptic potential

TEA:

Tetraethylammonium chloride

TTX:

Tetrodotoxin

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Acknowledgements

This work was partially supported by CSIC (Proyecto de Iniciación to F.S.). V. Comas was supported by a contract under a CSIC I+D grant to O.Macadar. The travel of Drs. O. Macadar and W. Buño was funded by a grant from Programa de Colaboración Internacional con Hispanoamérica, Ministerio de Educación y Ciencia/Consejo Superior de Investigación Científica, Spain. Special thanks to Dr. Ana Silva for critical reading of the manuscript. The experiments comply with the “Principles of Animal Care”, publication no. 86–23, revised in 1985, of The National Institutes of Health and also with the guidelines of the Comisión Honoraria de Experimentación Animal, Universidad de la República, Uruguay.

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Authors and Affiliations

  1. Unidad Asociada Neurofisiologia-IIBCE, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay

    Felipe Sierra

  2. Dpto. de Neurofisiología, Instituto de Investigaciones Biológicas Clemente Estable, Avda. Italia 3318, 11600, Montevideo, Uruguay

    Felipe Sierra, Virginia Comas & Omar Macadar

  3. Instituto Cajal, CSIC, Madrid, Spain

    Washington Buño

Authors
  1. Felipe Sierra
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  2. Virginia Comas
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  3. Washington Buño
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  4. Omar Macadar
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Correspondence to Felipe Sierra.

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Sierra, F., Comas, V., Buño, W. et al. Sodium-dependent plateau potentials in electrocytes of the electric fish Gymnotus carapo. J Comp Physiol A 191, 1–11 (2005). https://doi.org/10.1007/s00359-004-0567-7

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  • DOI: https://doi.org/10.1007/s00359-004-0567-7

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