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
DOIs
StatePublished - 1997

Keywords

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

ASJC Scopus subject areas

  • Neuroscience(all)

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