Electroretinography (ERG) in the wild giant panda (Ailuropoda melanoleuca)

Abstract

Purpose: Using a quick electroretinography (ERG) protocol for rapid assessment of the retinal function of wild giant pandas (Ailuropoda melanoleuca) performed in field conditions to demonstrate the range of ERG recordings in giant pandas of unknown retinal status.

Animals studied: Nine free range giant pandas.

Procedure: All the giant pandas were anesthetized using an intramuscular dexMTZ injection, which is a combination of dexmedetomidine and tiletamine-zolazepam. After 20 mins of dark adaptation, scotopic ERGs were obtained by using three flash intensities: -25 dB (0.0087 cd·s/m² ), 0 dB (2.75 cd·s/m² ), and +5 dB (8.7 cd·s/m² ). Next, photopic ERGs were acquired using a single flash protocol with a flash intensity of 3.0 cd·s/m² after 10 minutes of light adaptation.

Results: In scotopic ERG at 0.0087 cd·s/m² , mean b-wave amplitude and peak time were 82.26 µV (SD ± 16.65 and 95% CI 68.33-96.18) and 66.97 ms (SD ± 10.86 and 95% CI 57.90-76.05), respectively. This flash intensity was below a-wave threshold and resulted in b waves with greater peak times compared to those with higher intensities. At 2.75 cd·s/m² , the mean a-wave amplitude and peak time were 53.95 µV (SD ± 11.63 and 95% CI 44.23-63.67) and 16.13 ms (SD ± 2.62 and 95% CI 13.94-18.31), and mean b-wave amplitude and peak time were 119.57 µV (SD ± 15.54 and 95% CI 106.57-132.56) and 32.00 ms (SD ± 6.47 and 95% CI 26.59-37.41). At 8.7 cd·s/m² , the mean a-wave amplitude and peak time were 58.85 µV (SD ± 14.90 and 95% CI 46.39-71.31) and 15.59 ms (SD ± 2.63 and 95% CI 13.40-17.79), and the mean b-wave amplitude and peak time were 132.97 µV (SD ± 22.11 and 95% CI 114.48-151.46) and 32.66 ms (SD ± 6.87 and 95% CI 26.91-38.40). In photopic ERG at 2.75 cd·s/m² , the mean a-wave amplitude and peak time were 62.08 µV (SD ± 16.61 and 95% CI 48.19-75.97) and 16.28 ms (SD ± 0.90 and 95% CI 15.53-17.03), and the mean b-wave amplitude and peak time were 214.93 µV (SD ± 70.41 and 95% CI 156.07-273.80) and 33.09 ms (SD ± 1.27 and 95% CI 32.03-34.15).

Conclusion: Using a portable ERG system with a brief ERG protocol to perform electroretinographies in wild giant pandas is a practical, useful, and reliable method for the rapid assessment of their retinal function.

Keywords: ERG; giant panda; retinal function; vision.