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 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 |
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Keywords
- electroretinogram
- inactivation
- murine rod responses
- photoresponse recovery
- phototransduction
- rod photoreceptors
ASJC Scopus subject areas
- Neuroscience(all)
Cite this
Recovery phase of the murine rod photoresponse reconstructed from electroretinographic recordings. / Lyubarsky, Arkady L.; Pugh Jr, Edward N.
In: Journal of Neuroscience, Vol. 16, No. 2, 15.01.1996, p. 563-571.Research output: Contribution to journal › Article
}
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 -