June 2017
Volume 58, Issue 8
Open Access
ARVO Annual Meeting Abstract  |   June 2017
Contributions of Second- and Third-Order Retinal Neurons to Cone Electroretinograms after Loss of Rod Function in Rhodopsin P347L Transgenic Rabbits
Author Affiliations & Notes
  • Taro Kominami
    Ophthalmology, Nagoya University Graduate School of Medicine, Nagoya, Japan
  • Shinji Ueno
    Ophthalmology, Nagoya University Graduate School of Medicine, Nagoya, Japan
  • Satoshi Okado
    Ophthalmology, Nagoya University Graduate School of Medicine, Nagoya, Japan
  • Ayami Nakanishi
    Ophthalmology, Nagoya University Graduate School of Medicine, Nagoya, Japan
  • Mineo Kondo
    Ophthalmology, Mie University Graduate School of Medicine, Tsu, Japan
  • Hiroko Terasaki
    Ophthalmology, Nagoya University Graduate School of Medicine, Nagoya, Japan
  • Footnotes
    Commercial Relationships   Taro Kominami, None; Shinji Ueno, None; Satoshi Okado, None; Ayami Nakanishi, None; Mineo Kondo, None; Hiroko Terasaki, Nidek (P)
  • Footnotes
    Support  None
Investigative Ophthalmology & Visual Science June 2017, Vol.58, 5350. doi:
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      Taro Kominami, Shinji Ueno, Satoshi Okado, Ayami Nakanishi, Mineo Kondo, Hiroko Terasaki; Contributions of Second- and Third-Order Retinal Neurons to Cone Electroretinograms after Loss of Rod Function in Rhodopsin P347L Transgenic Rabbits. Invest. Ophthalmol. Vis. Sci. 2017;58(8):5350.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : To determine the contribution of second- and third-order retinal neurons to the photopic electroretinograms (ERGs) after the degeneration of the rods in rhodopsin P347L transgenic rabbits (Tg).

Methods :
Four wild type rabbits (WT) and four Tg rabbits were studied at 18 months-of-age. The photopic ERGs elicited at stimulus onset and offset were analyzed. To block different retinal pathways, 2-amino-4-phosphonobutyric acid (APB) and 6-cyano-7-nitroquinoxaline-2, 3 (1H,4H)-dione (CNQX), and tetrodotoxin (TTX) and N-methyl-DL-aspartic acid (NMDA) were injected intravitreally. Digital subtraction of the post-drug ERGs from the pre-drug ERGs was used to determine the contributions of the ON-components blocked by APB, the OFF-components blocked by CNQX, and the third-order neurons blocked by TTX+NMDA.

Results :
Contribution of the cone photoreceptors to the photopic ERGs in Tg rabbits was about 10% of that in WT rabbits. The amplitudes of the positive waves of the ON-components at stimulus onset in Tg rabbits were about one-half as large as those in WT. On the other hand, the amplitudes of the positive waves of the OFF-components at stimulus offset in Tg rabbits were about 1.4 to 2.3 times larger than those in WT. Tg rabbits had a positive wave at stimulus offset which was reduced after the TTX+NMDA injection.

Conclusions :
A reduced ON-component and an augmented OFF-component with abnormal responses of the third-order neurons contributed to the cone ERGs after the loss of rod function in Tg rabbits. Our results suggest a complex synaptic remodeling of the residual retinal cells in the advanced stage of Tg rabbits.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.

 

Pre-drug ERGs recorded from 4 WT rabbits (left columns) and 4 Tg rabbits (right columns) elicited by long-duration stimuli (A), saw-tooth rapid-ON stimuli (B), and saw-tooth rapid-OFF stimuli (C). The stimulus intensities were 2.5, 2.0 and 1.5 log cd/m2. The average ERG waveforms (black lines) are superimposed on ERG waveforms of each rabbit (grey lines). The stimulus markers are shown as grey lines beneath each ERG waveform. Arrow shows enhanced OFF responses in Tg rabbits.

Pre-drug ERGs recorded from 4 WT rabbits (left columns) and 4 Tg rabbits (right columns) elicited by long-duration stimuli (A), saw-tooth rapid-ON stimuli (B), and saw-tooth rapid-OFF stimuli (C). The stimulus intensities were 2.5, 2.0 and 1.5 log cd/m2. The average ERG waveforms (black lines) are superimposed on ERG waveforms of each rabbit (grey lines). The stimulus markers are shown as grey lines beneath each ERG waveform. Arrow shows enhanced OFF responses in Tg rabbits.

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