Cone photoreceptors respond to their own glutamate release in the tiger salamander

Serge Picaud, Hans P Larsson, David P. Wellis, Harold Lecar, Frank Werblin

Research output: Contribution to journalArticle

70 Citations (Scopus)

Abstract

Pulse-like currents resembling miniature postsynaptic currents were recorded in patch-clamped isolated cones from the tiger salamander retina. The events were absent in isolated cones without synaptic terminals. The frequency of events was increased by either raising the osmotic pressure or depolarizing the cell. It was decreased by the application of either glutamate or the glutamate-transport blockers dihydrokainate and D,L-threo- 3-hydroxyaspartate. The events required external Na+ for which Li+ could not substitute. The reversal potential of these currents followed the equilibrium potential for Cl- when internal Cl- concentration was changed. Thus, these miniature currents appear to represent the presynaptic activation of the glutamate receptor with glutamate transporter-like pharmacology, caused by the photoreceptor's own vesicular glutamate release. Using a noninvasive method to preserve the intracellular Cl- concentration, we showed that glutamate elicits an outward current in isolated cones. Fluorescence of the membrane-permeable form of fura-2 was used to monitor Ca2+ entry at the cone terminal as a measure of membrane depolarization. The increase in intracellular Ca2+ concentration, elicited by puff application of 30 mM KCl, was completely suppressed in the presence of 100 μM glutamate. Puff application of glutamate alone had no measurable depolarizing effect. These results suggest that the equilibrium potential for Cl-, E(Cl), was more negative than the activation range for Ca2+ channels and that glutamate elicited an outward current, hyperpolarizing the cones.

Original languageEnglish
Pages (from-to)9417-9421
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Volume92
Issue number20
DOIs
StatePublished - Sep 26 1995
Externally publishedYes

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Ambystoma
Retinal Cone Photoreceptor Cells
Glutamic Acid
Amino Acid Transport System X-AG
Synaptic Potentials
Membranes
Osmotic Pressure
Presynaptic Terminals
Glutamate Receptors
Retina
Fluorescence
Pharmacology

Keywords

  • Cl channel
  • presynaptic
  • receptor
  • retina
  • transporter

ASJC Scopus subject areas

  • Genetics
  • General

Cite this

Cone photoreceptors respond to their own glutamate release in the tiger salamander. / Picaud, Serge; Larsson, Hans P; Wellis, David P.; Lecar, Harold; Werblin, Frank.

In: Proceedings of the National Academy of Sciences of the United States of America, Vol. 92, No. 20, 26.09.1995, p. 9417-9421.

Research output: Contribution to journalArticle

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