### 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 50-10^{5} 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 language | English (US) |
---|---|

Pages (from-to) | 563-571 |

Number of pages | 9 |

Journal | Journal of Neuroscience |

Volume | 16 |

Issue number | 2 |

State | Published - Jan 15 1996 |

Externally published | Yes |

### Fingerprint

### Keywords

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

### ASJC Scopus subject areas

- Neuroscience(all)

### Cite this

*Journal of Neuroscience*,

*16*(2), 563-571.

**Recovery phase of the murine rod photoresponse reconstructed from electroretinographic recordings.** / Lyubarsky, Arkady L.; Pugh Jr, Edward N.

Research output: Contribution to journal › Article

*Journal of Neuroscience*, vol. 16, no. 2, pp. 563-571.

}

TY - JOUR

T1 - Recovery phase of the murine rod photoresponse reconstructed from electroretinographic recordings

AU - Lyubarsky, Arkady L.

AU - Pugh Jr, Edward N

PY - 1996/1/15

Y1 - 1996/1/15

N2 - 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.

AB - 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.

KW - electroretinogram

KW - inactivation

KW - murine rod responses

KW - photoresponse recovery

KW - phototransduction

KW - rod photoreceptors

UR - http://www.scopus.com/inward/record.url?scp=0030050756&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0030050756&partnerID=8YFLogxK

M3 - Article

C2 - 8551340

AN - SCOPUS:0030050756

VL - 16

SP - 563

EP - 571

JO - Journal of Neuroscience

JF - Journal of Neuroscience

SN - 0270-6474

IS - 2

ER -