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C. Balaratnasingam, W. H. Morgan, L. Bass, G. Matich, S. J. Cringle, D.-Y. Yu; Axonal Transport and Cytoskeletal Changes in the Laminar Regions Following Elevated Intraocular Pressure. Invest. Ophthalmol. Vis. Sci. 2007;48(13):3298.
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To investigate if axonal cytoskeleton changes occurred in the pre laminar, laminar and post laminar regions of the pig optic nerve after an acute increase in intraocular pressure (IOP) and whether this corresponded with axonal transport abnormalities.
Six Sus Scrofa pigs were used. The left eye IOP was elevated to 40-45 mmHg for 6 hours and the right eye IOP was maintained between 10-15 mmHg. Rhodamine-ß-Isothiocyanate (RITC) was injected into the vitreous of each eye at the beginning of the experiment to study axonal transport. Following euthanasia, optic nerves were enucleated and subjected to axonal transport and cytoskeleton studies. Antibodies to phosphorylated neurofilament heavy (NFHp), phosphorylation-independent neurofilament heavy (NFH), neurofilament light (NFL), neurofilament medium (NFM), microtubule and microtubule-associated protein (MAP) were used to study the axonal cytoskeleton. Montages of confocal microscopy images were quantitatively analysed to investigate simultaneous changes in axonal transport and cytoskeletal proteins in the laminar regions in both the high IOP and control eyes.
The change in RITC intensity within and 0.4 mm distal to the lamina cribrosa was significantly different in the high IOP eye implying that axonal transport was reduced in these regions. NFHp, NFM and NFH were significantly reduced in the pre laminar, laminar and post laminar regions in the optic nerve of the high IOP eye. NFL was only reduced in the pre laminar region. There was no difference in MAP and tubulin staining.
Elevated IOP induced both axonal transport and cytoskeleton changes in the optic nerve head. Changes to the cytoskeleton may contribute to axonal transport abnormalities occurring in elevated IOP.
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