Pigmented and albino rats differ in their responses to moderate, acute and reversible intraocular pressure elevation.

Abstract

To compare the electrophysiological and morphological responses to acute, moderately elevated intraocular pressure (IOP) in Sprague-Dawley (SD), Long-Evans (LE) and Brown Norway (BN) rat eyes. Eleven-week-old SD (n=5), LE (n=5) and BN (n=5) rats were used. Scotopic threshold responses (STRs), Maxwellian flash electroretinograms (ERGs) or ultrahigh-resolution optical coherence tomography (UHR-OCT) images of the rat retinas were collected from both eyes before, during and after IOP elevation of one eye. IOP was raised to ~35mmHg for 1h using a vascular loop, while the other eye served as a control. STRs, ERGs and UHR-OCT images were acquired on 3days separated by 1day of no experimental manipulation. There were no significant differences between species in baseline electroretinography. However, during IOP elevation, peak positive STR amplitudes in LE (mean±standard deviation 259±124µV) and BN (228±96µV) rats were about fourfold higher than those in SD rats (56±46µV) rats (p=0.0002 for both). Similarly, during elevated IOP, ERG b-wave amplitudes were twofold higher in LE and BN rats compared to those of SD rats (947±129µV and 892±184µV, vs 427±138µV; p=0.0002 for both). UHR-OCT images showed backward bowing in all groups during IOP elevation, with a return to typical form about 30min after IOP elevation. Differences in the loop-induced responses between the strains are likely due to different inherent retinal morphology and physiology.