Rod photoreceptor activation and deactivation in early-stage diabetic eye disease

McAnany, J. Jason; Park, Jason C

doi:10.1007/s10633-023-09925-y

Cited by 3 publications

(1 citation statement)

References 38 publications

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“…The use of a dim stimulus makes our method considerably easier for the volunteer to tolerate than methods using a paired flash protocol with equally bright CF and PF, both because it requires presentation of half as many unpleasant flashes per trial and because the necessary delay between trials is shorter. That said, the model frequently fit to recovery data from bright flashes 32 , 35 – 38 is mathematically similar to Equation 1b and, notably, assumes s Q = 2, so our model is certainly extensible to CFs of any intensity—however, for the reasons noted above, Q is unlikely to be stable over a wide range of CFs.…”

Section: Discussionmentioning

confidence: 94%

A Simplified Model of Activation and Deactivation of Human Rod Phototransduction—An Electroretinographic Study

Akula,

Lancos,

AlWattar

et al. 2023

Invest. Ophthalmol. Vis. Sci.

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Purpose To test the hypothesis that a simple model having properties consistent with activation and deactivation in the rod approximates the whole time course of the photoresponse. Methods Routinely, an exponential of the form f = α ·(1 – exp(–( τ ·( t – t eff ) s –1 ))), with amplitude α , rate constant τ (often scaled by intensity), irreducible delay t eff , and time exponent s –1, is fit to the early period of the flash electroretinogram. Notably, s (an integer) represents the three integrating stages in the rod amplification cascade (rhodopsin isomerization, transducin activation, and cGMP hydrolysis). The time course of the photoresponse to a 0.17 cd·s·m −2 conditioning flash (CF) was determined in 21 healthy eyes by presenting the CF plus a bright probe flash (PF) in tandem, separated by interstimulus intervals (ISIs) of 0.01 to 1.4 seconds, and calculating the proportion of the PF a -wave suppressed by the CF at each ISI. To test if similar kinetics describe deactivation, difference of exponential (DoE) functions with common α and t eff parameters, respective rate constants for the initiation ( I ) and quenching ( Q ) phases of the response, and specified values of s ( s I , s Q ), were compared to the photoresponse time course. Results As hypothesized, the optimal values of s I and s Q were 3 and 2, respectively. Mean ± SD α was 0.80 ± 0.066, I was 7700 ± 2400 m 2 ·cd –1 ·s –3 , and Q was 1.4 ± 0.47 s –1 . Overall, r 2 was 0.93. Conclusions A method, including a DoE model with just three free parameters ( α , I , Q ), that robustly captures the magnitude and time-constants of the complete rod response, was produced. Only two steps integrate to quench the rod photoresponse.

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Section: Discussionmentioning

confidence: 94%