Chloride equilibrium potential in salamander cones

Wallace B Thoreson, Eric J. Bryson

Research output: Contribution to journalArticle

29 Citations (Scopus)

Abstract

Background: GABAergic inhibition and effects of intracellular chloride ions on calcium channel activity have been proposed to regulate neurotransmission from photoreceptors. To assess the impact of these and other chloride-dependent mechanisms on release from cones, the chloride equilibrium potential (ECl) was determined in red-sensitive, large single cones from the tiger salamander retinal slice. Results: Whole cell recordings were done using gramicidin perforated patch techniques to maintain endogenous Cl- levels. Membrane potentials were corrected for liquid junction potentials. Cone resting potentials were found to average -46 mV. To measure ECl, we applied long depolarizing steps to activate the calcium-activated chloride current (ICl(Ca)) and then determined the reversal potential for the current component that was inhibited by the Cl- channel blocker, niflumic acid. With this method, ECl was found to average -46 mV. In a complementary approach, we used a Cl-sensitive dye, MEQ, to measure the Cl- flux produced by depolarization with elevated concentrations of K+. The membrane potentials produced by the various high K+ solutions were measured in separate current clamp experiments. Consistent with electrophysiological experiments, MEQ fluorescence measurements indicated that ECl was below -36 mV. Conclusions: The results of this study indicate that ECl is close to the dark resting potential. This will minimize the impact of chloride-dependent presynaptic mechanisms in cone terminals involving GABAa receptors, glutamate transporters and ICl(Ca).

Original languageEnglish (US)
Article number53
JournalBMC Neuroscience
Volume5
DOIs
StatePublished - Dec 5 2004

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Urodela
Membrane Potentials
Chlorides
GABA Agents
Niflumic Acid
Ambystoma
Amino Acid Transport System X-AG
Gramicidin
Calcium Chloride
Patch-Clamp Techniques
Calcium Channels
Synaptic Transmission
Coloring Agents
Fluorescence

ASJC Scopus subject areas

  • Medicine(all)
  • Clinical Neurology
  • Neuroscience(all)
  • Cellular and Molecular Neuroscience

Cite this

Chloride equilibrium potential in salamander cones. / Thoreson, Wallace B; Bryson, Eric J.

In: BMC Neuroscience, Vol. 5, 53, 05.12.2004.

Research output: Contribution to journalArticle

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