Elsevier

Vision Research

Volume 101, August 2014, Pages 108-117
Vision Research

Ex vivo ERG analysis of photoreceptors using an in vivo ERG system

https://doi.org/10.1016/j.visres.2014.06.003Get rights and content
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Highlights

  • Commercial in vivo ERG system can be used for transretinal rod and cone recordings.

  • Rod and cone ERG a- and b-waves are comparable in ex vivo and in vivo recordings.

  • Flash responses are slower and the oscillatory potentials are attenuated ex vivo.

  • The estimated amplification constant is >2-fold larger in mouse rods than in cones.

  • Light funneling in vivo might account for ∼3-fold increased photon capture in cones.

Abstract

The Function of the retina and effects of drugs on it can be assessed by recording transretinal voltage across isolated retina that is perfused with physiological medium. However, building ex vivo ERG apparatus requires substantial amount of time, resources and expertise. Here we adapted a commercial in vivo ERG system for transretinal ERG recordings from rod and cone photoreceptors and compared rod and cone signaling between ex vivo and in vivo environments. We found that the rod and cone a- and b-waves recorded with the transretinal ERG adapter and a standard in vivo ERG system are comparable to those obtained from live anesthetized animals. However, ex vivo responses are somewhat slower and their oscillatory potentials are suppressed as compared to those recorded in vivo. We found that rod amplification constant (A) was comparable between ex vivo and in vivo conditions, ∼10–30 s−2 depending on the choice of response normalization. We estimate that the A in cones is between 3 and 6 s−2 in ex vivo conditions and by assuming equal A in vivo we arrive to light funnelling factor of 3 for cones in the mouse retina. The ex vivo ERG adapter provides a simple and affordable alternative to designing a custom-built transretinal recordings setup for the study of photoreceptors. Our results provide a roadmap to the rigorous quantitative analysis of rod and cone responses made possible with such a system.

Abbreviations

ERG
electroretinography
Gnat1
rod G protein transducin
SNR
signal-to-noise ratio
LED
light-emitting diode
DL-AP4 or APB
DL-2-amino-4-phosphonobutyric acid
PBS
phosphate-buffered saline

Keywords

Electroretinogram
Transretinal ERG
a-Wave
b-Wave
Photoreceptor

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