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Author Bissig, David
Title Predicting vision loss in healthy aging with manganese-enhanced mri of the rat eye [electronic resource] / by David Bissig.
Publication Info. 2013.
Location Call No. Status Notes
 Libraries Electronic Books  Electronic Resource - WSU ETD    AVAIL. ONLINE
Description 115 p. : ill.
Note Advisor: Bruce A. Berkowitz.
Thesis Thesis (Ph.D.) -- Wayne State University, 2013.
Summary In healthy aging, visual function declines throughout adulthood. Age-related changes in neuronal ion homeostasis -- specifically, increased Ca²⁺ influx through L-type voltage gated calcium channels (L-VGCCs) -- are believed to contribute to certain functional declines, but this possibility has not yet been tested in the neural retina. In young, mid- and old adult Long-Evans rats, we compared visual function (optokinetic tracking), as well as retinal physiology and eye morphology (Mn²⁺-enhanced MRI (MEMRI), which uses neuronal Mn²⁺ uptake as a marker of Ca²⁺ influx). We documented significant age-related decreases in visual performance and increases in retinal ion influx. We confirmed that Mn²⁺ uptake was regulated by L-VGCC using systemic and topical application of the L-VGCC antagonist nifedipine, and discovered an age-related change in sensitivity to L-VGCC blocker diltiazem. Based on Western blot studies, we find this sensitivity change to be consistent with the age-dependant appearance of drug-insensitive L-VGCC isoforms. Longitudinally, rats starting the study with relatively high retinal Mn²⁺ uptake, compared to other cohort members, experienced significantly greater declines in contrast sensitivity in the ̃4.5 mo following MRI. Independent of that relationship, rats starting the study with relatively large eyes experienced significantly greater declines in contrast sensitivity. The latter finding suggests that particularly rapid juvenile or young-adult growth is a risk factor for particularly rapid senescence. Longitudinally, we found no evidence of retinal volume loss, and found that changes in retinal volume were not correlated with changes in visual function -- suggesting that age-related vision declines cannot be explained by neuron loss. In summary, our longitudinal studies identify two previously-unknown risk factors for age-related vision declines: rapid eye growth in early life, and age-related changes in L-VGCC-dependent retinal ion physiology.
Subject Neurosciences
Added Title Wayne State University thesis (Ph.D.) : Anatomy and Cell Biology
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