Recovery phase of the murine rod photoresponse reconstructed from electroretinographic recordings

Arkady L. Lyubarsky, Edward N Pugh Jr

Research output: Contribution to journalArticle

193 Scopus citations

Abstract

The activation and recovery phases of the murine rod photoresponse were determined from corneal electroretinograms (ERGs) obtained in response to pairs of full-field flashes producing 50-105 photoisomerized rhodopsins (R*) per rod. The a-wave component of the ERG in response to the initial flash provided a well established measure of the activation phase of the red response. The amplitude of the a-wave response to an intense second flash (45,000 R*) delivered 0.2-5 seconds (s) after the first flash was used to reconstruct the recovery phase of the response. For 160-3000 R* rod-1, recovery curves were isomorphic, translating on the time axis such that each e-fold increase in R* produced an incremental recovery delay of τ(c) = 210 ± 50 ms (mean ± SD). For initial flashes producing >3000 R*, recovery curves lost their initial isomorphism and half-times had intensity dependence exceeding 1 s per e-fold increase in R*. We conclude that for flashes producing <3000 R*, the effective lifetime of these R* is not >210 ms. Two extant and non-mutually exclusive hypotheses are discussed that can account for the sharp increase in recovery times from flashes producing >3000 R*. They are as follows: (1) ~0.03% of R* have a lifetime exceeding 1 s; and (2) the γ subunit of phosphodiesterase (PDE(γ)) serves as a GTPase- activating factor, and 3000 R* produce sufficient activated G-protein (G*) to exceed the total quantity of PDE(γ) subunits such that excess G* must wait for unoccupied PDE(γ) to inactivate via GTP hydrolysis.

Original languageEnglish (US)
Pages (from-to)563-571
Number of pages9
JournalJournal of Neuroscience
Volume16
Issue number2
StatePublished - Jan 15 1996
Externally publishedYes

Keywords

  • electroretinogram
  • inactivation
  • murine rod responses
  • photoresponse recovery
  • phototransduction
  • rod photoreceptors

ASJC Scopus subject areas

  • Neuroscience(all)

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