Genetically heterogeneous mice show age-related vision deficits not related to increased rod cell L-type calcium channel function in vivo

Abstract

Visual performance declines over time in humans and 2-18 mo outbred Long-Evans (LE) rats; vision is maintained in inbred 2- 18 mo C57BL/6 (B6) mice. Increased rod L-type calcium channel (LTCC) function predicts visual decline in LE rats but does not occur in B6 mice. Genetic diversity may contribute to rod LTCC function escalation time. To test this hypothesis, 4 and 18 mo genetically heterogeneous UM-HET3 mice were studied. Rod LTCC function (manganese-enhanced MRI), and ocular anatomy (MRI, optical coherence tomography, were measured in vivo. Light-evoked subretinal space (SRS) and choroid thickness changes were measured (diffusion-weighted MRI). Visual performance declined over time in the absence of i) increased rod LTCC function, ii) changes in light-dependent expansion of the SRS and choroidal thickness, and iii) retinal thinning. Aging changed anterior and vitreous chambers axial length, and decreased light-stimulated choroidal expansion. Species differences appear to contribute to the LTCC function differences. Aging-related declines in vision in the UM-HET3 mice deserve more attention than they have received so far.

Novel QUEST MRI In Vivo Measurement of Noise-induced Oxidative Stress in the Cochlea

“…In this study, we test the hypothesis that harmful noise-induced oxidative stress can be measured in vivo using QUEST MRI 13–15 . Sprague Dawley rats were exposed to acoustic overstimulation to generate oxidative stress and were studied before and after anti-oxidant treatment with a combination of two anti-oxidants (AO’s): methylene blue (an alternative electron transporter that inhibits superoxide radical formation by mitochondria and oxidases) and α-lipoic acid (a free radical scavenger) 14,17,18 . The results were compared with a “gold standard” biomarker for oxidative stress: ex vivo whole mount preparations of the cochlea labeled for heme oxygenase I 19 ; hair cell loss and hearing loss were also evaluated as other markers 20 .…”