Desensitization of the mGluR6 transduction current in tiger salamander On bipolar cells

Scott Nawy

Research output: Contribution to journalArticle

32 Citations (Scopus)

Abstract

Light depolarizes retinal On bipolar cells, opening the cation-selective channels that are responsible for producing the synaptic current. In this study, the basic features of light-induced signals were mimicked by bathing slices of salamander retina with an agonist for the mGluR6 receptor that is expressed on the dendrites of On cells, and then displacing the agonist with the mGluR6 antagonist (RS)-a-cyclopropyl-4-phosphonophenylglycine (CPPG). The transduction current that is activated by this protocol rapidly shuts off, or desensitizes. Desensitization was highly correlated with the concentration and the type of Ca2+ buffer that was dialysed into the cell: When Ca2+ buffering was minimized by dialysing cells with 0.5 mM EGTA, the steady-state response was reduced to approximately 40% of the peak response. Buffering with 10 mM EGTA reduced desensitization, while BAPTA completely eliminated it. Removing external Ca2+ also prevented desensitization, suggesting that entry of Ca2+ through the transduction channel provides the trigger. The time course of desensitization was measured by using a voltage jump protocol to rapidly increase Ca2+ influx, and could be fitted with a single time constant on the order of 1 s, in good agreement with previously published rates of desensitization to steps of light in this species. It is proposed that Ca2+-dependent shut-off of the On bipolar cell transduction current may contribute to the conversion of sustained to transient light responses that predominate in the inner retina.

Original languageEnglish (US)
Pages (from-to)137-146
Number of pages10
JournalJournal of Physiology
Volume558
Issue number1
DOIs
StatePublished - Jul 1 2004

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Ambystoma
Light
Egtazic Acid
Retina
Retinal Bipolar Cells
Urodela
Dendrites
Cations
Buffers
metabotropic glutamate receptor 6

ASJC Scopus subject areas

  • Physiology

Cite this

Desensitization of the mGluR6 transduction current in tiger salamander On bipolar cells. / Nawy, Scott.

In: Journal of Physiology, Vol. 558, No. 1, 01.07.2004, p. 137-146.

Research output: Contribution to journalArticle

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