Tetrodotoxin-resistant sodium channels contribute to directional responses in starburst amacrine cells

Nicholas W. Oesch, William Taylor

Research output: Contribution to journalArticle

32 Citations (Scopus)

Abstract

The biophysical mechanisms that give rise to direction selectivity in the retina remain uncertain. Current evidence suggests that the directional signal first arises within the dendrites of starburst amacrine cells (SBACs). Two models have been proposed to explain this phenomenon, one based on mutual inhibitory interactions between SBACs, and the other positing an intrinsic dendritic mechanism requiring a voltage-gradient depolarizing towards the dendritic tips. We tested these models by recording current and voltage responses to visual stimuli in SBACs. In agreement with previous work, we found that the excitatory currents in the SBACs were directional, and remained directional when GABA receptors were blocked. Contrary to the mutual-inhibitory model, stimuli that produce strong directional signals in ganglion cells failed to reveal a significant inhibitory input to SBACs. Suppression of the tonic excitatory conductance, proposed to generate the dendritic voltagegradient required for the dendrite autonomous model, failed to eliminate the directional signal in SBACs. However, selective block of tetrodotoxin-resistant sodium channels did reduce the strength of the directional excitatory signal in the SBACs. These results indicate that current models of direction-selectivity in the SBACs are inadequate, and suggest that voltage-gated excitatory channels, specifically tetrodotoxin-resistant sodium channels, are important elements in directional signaling. This is the first physiological evidence that tetrodotoxin-resistant sodium channels play a role in retinal information processing.

Original languageEnglish (US)
Article numbere12447
JournalPLoS One
Volume5
Issue number8
DOIs
StatePublished - 2010

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Amacrine Cells
tetrodotoxin
sodium channels
Sodium Channels
Tetrodotoxin
cells
Electric potential
Dendrites
dendrites
GABA Receptors
Automatic Data Processing
Ganglia
retina
Retina

ASJC Scopus subject areas

  • Agricultural and Biological Sciences(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Medicine(all)

Cite this

Tetrodotoxin-resistant sodium channels contribute to directional responses in starburst amacrine cells. / Oesch, Nicholas W.; Taylor, William.

In: PLoS One, Vol. 5, No. 8, e12447, 2010.

Research output: Contribution to journalArticle

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