Temporal properties of flicker ERGs in a transgenic rabbit model of retinitis pigmentosa

Abstract

Purpose : To determine the effects of a remodeled inner retina on the flicker ERGs in a rabbit eye at an advanced stage of retinal degeneration.

Methods :
Six wild-type (WT) and four rhodopsin P347L transgenic (Tg) rabbits were studied at 18-months of age. Flicker ERGs were elicited by sinusoidal stimuli at frequencies of 3.906 Hz to 50.781 Hz in 13 steps. To block ON and OFF retinal pathways, 2-amino-4-phosphonobutyric acid (APB), and 6-cyano-7-nitroquinoxaline-2, 3(1H, 4H)-dione (CNQX) were injected intravitreally. The amplitudes and phases of the fundamental components of the pre- and post-drug ERGs were analyzed. The postsynaptic APB (ON-) and CNQX (OFF-) sensitive components were determined by examining the phase and amplitude vectors.

Results : The temporal properties of the Tg rabbits were different from those of the WT rabbits and had unique features; at frequency of 3.906 Hz, the amplitude was depressed but it increased by more than 3.5-fold at 15.625 Hz. The reduction of the amplitude at 3.906 Hz in Tg rabbits was caused by a cancelation of the ON and OFF components by a phase difference of 180°. On the other hand, an increase in the amplitude at 15.625 Hz in Tg rabbits was caused by the summation of the ON and OFF components which had an approximate 120° phase difference.

Conclusions : The temporal properties of the flicker ERGs of Tg rabbits were markedly affected by the remodeling of the retinal neurons. Evaluations of the flicker ERGs in RP eyes needs to be done with careful considerations of the current findings.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.