Enhancement of persistent sodium current by internal fluorescence in isolated hippocampal neurons.

Published

Journal Article

Following up on an earlier chance observation, voltage-dependent whole-cell currents were recorded from isolated hippocampal neurons filled with the fluorescent dyes Fluo-3 and Fura-red, that were intermittently excited by 488 nm laser light. In the absence of any ion channel blocking drugs, in most cells depolarizing voltage steps initially evoked only the 'Hodgkin-Huxley' type early, fast inward surge followed by sustained outward current. Over 5-20 min of intermittent electrical stimulation and laser-excited fluorescence pulses, a voltage-dependent, slowly inactivating inward current also appeared and grew, while sustained outward current diminished. When K(+) currents were blocked, a small persistent inward current was usually detectable immediately, and then it increased in amplitude. This current was blocked by tetrodotoxin (TTX) and it had current-voltage (I-V) characteristics of a persistent sodium current, I(Na,P). In cells not filled with dye but illuminated by laser, and in cells with dye but not illuminated, I(Na,P) remained small. There was a more than 12-fold difference in the maximal amplitude of I(Na, P) of fluorescent compared to non-fluorescent cells. Once induced, I(Na,P) decreased very slowly. Fluorescence increased the duration but not the amplitude of the transient Na(+) current, I(Na,T). With membrane potential clamped to a constant voltage, the laser-induced fluorescence did not evoke a membrane current. It is not certain whether fluorescence-induced I(Na,P) potentiation is related to photodynamic action.

Full Text

Duke Authors

Cited Authors

  • Somjen, GG

Published Date

  • December 1, 2000

Published In

Volume / Issue

  • 885 / 1

Start / End Page

  • 94 - 101

PubMed ID

  • 11121534

Pubmed Central ID

  • 11121534

International Standard Serial Number (ISSN)

  • 0006-8993

Digital Object Identifier (DOI)

  • 10.1016/s0006-8993(00)02947-4

Language

  • eng

Conference Location

  • Netherlands