Abstract
Purpose :
To standardize the amplitude and implicit time measurements of the flash and pattern electroretinograms (FERG and PERG, respectively) in healthy Lister hooded rats.
Methods :
Adult pigmented Lister hooded rats were deeply anesthetized and positioned 20 cm from the visual stimuli. Stainless steel needles were used as electrodes and properly positioned (cornea: +; ipsilateral temporal canthus: –; left hind limb: ground). FERG stimulus was a white strobe flash with different light intensities (in joules, J). For scotopic FERG acquisition, animals were dark-adapted overnight, and the amplitude (A) and implicit time (IT) of scotopic a- and b-waves (0.6J–40J), oscillatory potentials (OPs; 20J), scotopic c-wave (20J) and early receptor potential (ERP: R1 and R2; 40J) were calculated. Photopic FERG was registered with animals adapted to room light, and 20 individual responses (20J; 1 Hz) were averaged for b-wave measurement. Cones function was isolated with a flickering flash of 1.2J and 15Hz. PERG stimulus consisted on the contrast reversal of a checkerboard (15 rev/s, steady-state PERG), with constant mean luminance and varied spatial frequencies (0.018 – 0.585 cpd).
Results :
Increasing flash intensity generated higher wave amplitudes and shorter implicit times. With the lowest flash intensity (blue 0.6J), the negative a-wave was absent, appearing with white 0.6J flash (isolated rods function; A: 116.6 ± 26.88; IT: 19.4 ± 0.7043 ms). With 20J and 40J flashes, a- and b- deflections were divided into a1/ a2 and b1/b2, known to be related to cones and rods visual pathways, respectively. Scotopic c-wave (RPE function) parameters were A: 304.5 ± 52.08 µV; IT: 1494 ± 143.1 ms, and five OPs (inner retina) were isolated: O1–O5. ERP consisted on R1 (cones; A: 11.23 ± 10.96 ; IT: 0.1330 ± 0.0315 ms) and R2 (cones and rods; A: 84.24 ± 33.11 µV ; IT: 0.7833 ± 0.0945 ms). Photopic b-wave (A: 213.3 ± 77.3 µV; IT: 46.67 ± 2.251 ms) was followed by a negative deflection, the PhNR (A: 80.73 ± 27.43 µV; IT: 154.5 ± 12.37 ms). Photopic flicker amplitude was 15.9 ± 6.817 µV. Steady-state PERG amplitude depended on the stimulus spatial frequency, ranging from 8.111 ± 1.652 µV (0.018 cpd) to 2.055 ± 0.463 (0.585 cpd).
Conclusions :
A thorough characterization of ERG waveforms from a healthy pigmented rat strain was performed. The presented data will be useful for interlaboratory comparisons and in the context of retinal diseases.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.