title: Sodium-dependent plateau potentials in electrocytes of the electric fish Gymnotus carapo.
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 Ca(2+)-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.
authors.affiliation: Unidad Asociada Neurofisiologia-IIBCE, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay. fsierra@iibce.edu.uy
authors.forename: Felipe
authors.initials: F
authors.lastname: Sierra
authors.forename: Virginia
authors.initials: V
authors.lastname: Comas
authors.forename: Washington
authors.initials: W
authors.lastname: Buño
authors.forename: Omar
authors.initials: O
authors.lastname: Macadar
mesh_terms: D000200:Action Potentials / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D004553:Electric Conductivity; D004557:Electric Organ / Q000166:cytology* / Q000187:drug effects / Q000502:physiology*; D023702:Gymnotiformes / Q000502:physiology*; D066298:In Vitro Techniques; D017136:Ion Transport / Q000187:drug effects / Q000502:physiology*; D032342:Muscle Cells / Q000502:physiology; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000502:physiology; D012964:Sodium / Q000502:physiology*; D026941:Sodium Channel Blockers / Q000494:pharmacology; D015222:Sodium Channels / Q000187:drug effects / Q000502:physiology; D013779:Tetrodotoxin / Q000494:pharmacology
chemical_list: D015221:Potassium Channels; D026941:Sodium Channel Blockers; D015222:Sodium Channels; D013779:Tetrodotoxin; D012964:Sodium