Visual function in guinea pigs: behavior and electrophysiology

ABSTRACT

Clinical relevance

Guinea pig visual function is characterised based on behavioural and electrophysiological measures and retinal ganglion cell density is examined to further develop the guinea pig as a model of human ocular conditions.

Background

Guinea pigs are an important model of human ocular conditions. Here, guinea pig spatial frequency discrimination, pattern and full-field photopic electroretinography (ERG), and retinal ganglion cell distribution were investigated.

Methods

Adult guinea pigs (n = 6) were included. Optomotor responses to square-wave gratings from 0.3 to 2.4 cycles per degree (cpd) were assessed. Pattern ERG responses were recorded using square-wave gratings from 0.025 to 0.25 cpd at 100% contrast, alternating at a temporal frequency of 1.05 Hz. Full-field ERG responses were recorded using a 10.0 cd.s/m² flash. Ganglion cell density was determined histologically from retinal whole mounts.

Results

Maximum spatial frequency discrimination was 1.65 ± 0.49 cpd for stimuli rotating temporally to nasally and 0.75 ± 0.16 cpd for stimuli rotating nasally to temporally. For pattern ERG, a maximum amplitude of 3.50 ± 1.16 µV for the first negative to positive peak (N1P1) was elicited with a 0.025 cpd grating, and 2.5 ± 0.1 µV for the positive to second negative peak (P1N2) was elicited with a 0.05 cpd grating. For full-field ERG, a-wave amplitude was 19.2 ± 4.24 µV, b-wave amplitude was 33.6 ± 8.22 µV, and the PhNR was 24.0 ± 5.72 µV. Peak retinal ganglion cell density was 1621 ± 129 cells/mm², located 1–2 mm superior to the optic nerve head.

Conclusion

Guinea pigs show directional selectivity for stimuli moving in the temporal to the nasal visual field. Guinea pigs demonstrate a quantifiable PhNR in the full-field ERG and negative and positive waveforms in the pattern ERG. The visual streak is located in the superior retina.

KEYWORDS:

• Electroretinogram
• guinea pigs
• optomotor response
• retinal ganglion cells
• visual function

Acknowledgements

The authors thank Alan Burns for help with Delta Vision imaging, Krista Beach for help with immunohistochemistry, John Bauer for help with constructing the custom optokinetic drum, and Alexander Schill for help calibrating the pattern ERG stimulus.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This study was funded by NIH NEI [K08 EY022696 and P30 EY007551].