Axonal transport and cytoskeletal changes in the laminar regions after elevated intraocular pressure.
OBJECTIVE
To investigate the axonal cytoskeleton changes occurring in the prelaminar region, lamina cribrosa, and postlaminar region of the porcine optic nerve after an acute increase in intraocular pressure (IOP) and whether this corresponds with axonal transport abnormalities.


METHODS
Six white Landrace pigs were used. The left eye IOP was elevated to 40 to 45 mm Hg for 6 hours, and the right eye IOP was maintained between 10 and 15 mm Hg. Rhodamine-beta-isothiocyanate (RITC) was injected into the vitreous of each eye at the beginning of the experiment, to study axonal transport. After euthanasia, optic nerves were removed and prepared for 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 analyzed to investigate simultaneous changes in optic nerve axonal transport and cytoskeletal proteins in the high-IOP and control eyes.


RESULTS
Axonal transport of RITC was reduced in the prelaminar, lamina cribrosa, and proximal 400 mum of the postlaminar optic nerve regions in the high-IOP eye. NFHp, NFM, and NFH were significantly reduced in the prelaminar, lamina cribrosa, and proximal postlaminar regions in the high-IOP eye. No differences in NFL, MAP, and tubulin staining were detected.


CONCLUSIONS
Elevated IOP induced both axonal transport and cytoskeleton changes in the optic nerve head. Changes to the cytoskeleton may contribute to the axonal transport abnormalities that occur in elevated IOP.
Balaratnasingam
Chandrakumar
C
Centre for Ophthalmology and Visual Science, The University of Western Australia, Perth, Australia.
Morgan
William H
WH
Bass
Louise
L
Matich
Graeme
G
Cringle
Stephen J
SJ
Yu
Dao-Yi
DY
D000818:Animals; D001370:Axonal Transport / Q000502:physiology*; D001794:Blood Pressure; D003599:Cytoskeleton / Q000378:metabolism / Q000473:pathology*; D004195:Disease Models, Animal; D005260:Female; D005901:Glaucoma / Q000378:metabolism* / Q000473:pathology*; D007429:Intraocular Pressure / Q000502:physiology*; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D008954:Models, Biological; D016900:Neurofilament Proteins / Q000378:metabolism; D009898:Optic Disk / Q000378:metabolism / Q000473:pathology; D010100:Oxygen / Q000097:blood; D010766:Phosphorylation; D015203:Reproducibility of Results; D013194:Staining and Labeling; D034421:Sus scrofa; D014404:Tubulin / Q000378:metabolism
D008869:Microtubule-Associated Proteins; D016900:Neurofilament Proteins; D014404:Tubulin; C044882:neurofilament protein L; C061195:neurofilament protein M; D010100:Oxygen