Gain of rod to horizontal cell synaptic transfer: Relation to glutamate release and a dihydropyridine-sensitive calcium current

Paul Witkovsky, Yvonne Schmitz, Abram Akopian, David Krizaj, Daniel Tranchina

Research output: Contribution to journalArticle

Abstract

We related rod to horizontal cell synaptic transfer to glutamate release by rods. Simultaneous intracellular records were obtained from dark-adapted rod-horizontal cell pairs. Steady-state synaptic gain (defined as the ratio of horizontal cell voltage to red voltage evoked by the same light stimulus) was 3.35 ± 0.60 for dim flashes and 1.50 ± 0.03 for bright flashes. Under conditions of maintained illumination, there was a measurable increment of horizontal cell hyperpolarization for each light-induced increment of rod hyperpolarization over the full range of rod voltages. In separate experiments we studied glutamate release from an intact, light-responsive photoreceptor layer, from which in net retinal layers were removed. Steady light reduced glutamate release as a monotonic function of intensity; spectral sensitivity measures indicated that we monitored glutamate release from rods. The dependence of glutamate release on rod voltage was well fit by the activation function for a high-voltage-activated, dihydropyridine- sensitive L-type calcium current, suggesting a linear dependence of glutamate release on [Ca] in the synaptic terminal. A simple model incorporating this assumption accounts for the steady-state gain of the rod to horizontal cell synapse.

Original languageEnglish (US)
Pages (from-to)7297-7306
Number of pages10
JournalJournal of Neuroscience
Volume17
Issue number19
StatePublished - 1997

Fingerprint

Glutamic Acid
Calcium
Light
Presynaptic Terminals
Lighting
Synapses
1,4-dihydropyridine

Keywords

  • Calcium
  • Glutamate release
  • Horizontal cell
  • Photoreceptor
  • Rod
  • Synaptic gain
  • Xenopus

ASJC Scopus subject areas

  • Neuroscience(all)

Cite this

Gain of rod to horizontal cell synaptic transfer : Relation to glutamate release and a dihydropyridine-sensitive calcium current. / Witkovsky, Paul; Schmitz, Yvonne; Akopian, Abram; Krizaj, David; Tranchina, Daniel.

In: Journal of Neuroscience, Vol. 17, No. 19, 1997, p. 7297-7306.

Research output: Contribution to journalArticle

Witkovsky, Paul ; Schmitz, Yvonne ; Akopian, Abram ; Krizaj, David ; Tranchina, Daniel. / Gain of rod to horizontal cell synaptic transfer : Relation to glutamate release and a dihydropyridine-sensitive calcium current. In: Journal of Neuroscience. 1997 ; Vol. 17, No. 19. pp. 7297-7306.
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