dizocilpine-maleate and Optic-Nerve-Diseases

To investigate whether a recently described retinal ganglion cell (RGC) marker Rbpms (RNA binding protein with multiple splicing) could be used for RGC quantification in various models of RGC degeneration.. Optic nerve crush, excitotoxicity, and elevated intraocular pressure (IOP) rat models were used. Topographic analysis of Rbpms immunolabeling was performed on retinal wholemounts. Retrograde labelings with Fluorogold (FG) and III β-tubulin immunohistochemistry were compared.. In the optic nerve crush model, 37%, 87%, and 93% of Rbpms-positive cells were lost 1, 2, and 4 weeks, respectively. Significant loss of Rbpms-positive cells was noted 1 week after intravitreal injection of 12, 30, and 120 nmol N-methyl-d-aspartate (NMDA), whereas coinjection of 120 nmol of NMDA along with MK-801 increased the cell number from 10% to 59%. Over 95% of Rbpms-positive cells were FG- and III β-tubulin-positive after injury caused by optic nerve crush and NMDA injection. In rats with elevated IOP, induced by trabecular laser photocoagulation, there was a significant loss of Rbpms-positive cells compared with that of contralateral controls (P = 0.0004), and cumulative IOP elevation showed a strong linear relationship with the quantification of RGCs by Rbpms immunolabeling and retrograde labeling with FG. More than 99% of the remaining Rbpms-positive cells were double-labeled with FG.. Rbpms can reliably be used as an RGC marker for quantitative evaluation in rat models of RGC degeneration, regardless of the nature and the location of the primary site of the injury and the extent of neurodegeneration.

Topics: Animals; Biomarkers; Cell Count; Cell Survival; Disease Models, Animal; Dizocilpine Maleate; Fluorescent Antibody Technique, Indirect; Glaucoma; Intraocular Pressure; Male; N-Methylaspartate; Nerve Crush; Optic Nerve Diseases; Optic Nerve Injuries; Rats; Rats, Inbred BN; Rats, Wistar; Retinal Ganglion Cells; RNA-Binding Proteins; Stilbamidines; Tonometry, Ocular; Tubulin

A new experimental glaucoma model was developed by using an ex vivo rat retinal preparation to examine the effects of elevated hydrostatic pressure on retinal morphology and glutamine synthetase (GS) activity.. Ex vivo rat retinas were exposed to elevated hydrostatic pressure for 24 hours in the presence of glutamate or glutamate receptor antagonists and examined histologically. GS activity was assessed by colorimetric assay.. Pressure elevation induced axonal swelling in the nerve fiber layer. Axonal swelling was prevented by a combination of non-N-methyl-d-aspartate (non-NMDA) receptor antagonist and an NMDA receptor antagonist, indicating that the damage results from activation of both types of glutamate receptor. When glial function was preserved, the typical changes induced by glutamate consisted of reversible Müller cell swelling resulting from excessive glial glutamate uptake. The irreversible Müller cell swelling in hyperbaric conditions may indicate that pressure disrupts glutamate metabolism. Indeed, elevated pressure inhibited GS activity. In addition, glutamate exposure after termination of pressure exposure exhibited apparent Müller cell swelling.. These results suggest that the neural degeneration observed during pressure elevation is caused by impaired glial glutamate metabolism after uptake.

Topics: Animals; Axons; Disease Models, Animal; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Fluorescent Antibody Technique, Indirect; Glial Fibrillary Acidic Protein; Glutamate-Ammonia Ligase; Glutamic Acid; Hydrostatic Pressure; Male; Optic Disk; Optic Nerve Diseases; Rats; Rats, Sprague-Dawley; Receptors, Glutamate; Retinal Diseases; Retinal Ganglion Cells

To establish a rat model of acute increase in intraocular pressure (IOP) and to investigate the therapeutic window for protection against death of retinal ganglion cells (RGCs) by vaccination with glatiramer acetate (Cop-1) or by treatment with brimonidine or MK-801.. Animal study, laboratory investigation.. IOP was transiently increased in anesthetized Lewis rats by infusing normal saline (0.9%) into the anterior chamber of the eye for one hour. RGC survival was assessed one week and two weeks later by counting the RGCs retrogradely labeled with rhodamine dextran.. RGC survival.. IOP rose to 100 cm H(2)O (76 mm Hg) and returned to baseline after 24 hours. The RGC count decreased by 23% a week after the insult and by a further 7% after the second week. Vaccination with Cop-1 on the day of the insult prevented 50% of the IOP-induced RGC loss. Similar neuroprotection was achieved by daily intraperitoneal injections of brimonidine, but not with MK-801.. A transient increase in IOP to 100 cm H(2)O causes death of RGCs in rats. A single immunization with Cop-1 or daily injections of brimonidine protected up to 50% of potentially doomed RGCs from IOP-induced death, suggesting that not all of the cell death in the untreated model results from the IOP insult directly, but that some of it is caused by insult-induced environmental cytotoxicity, which is unrelated to glutamate toxicity or at least to NMDA receptors. These findings can be applied immediately as a basis for acute glaucoma therapy.

Topics: Acute Disease; Animals; Antihypertensive Agents; Brimonidine Tartrate; Cell Survival; Disease Models, Animal; Dizocilpine Maleate; Glatiramer Acetate; Immunization; Injections; Intraocular Pressure; Male; Neuroprotective Agents; Ocular Hypertension; Optic Nerve Diseases; Peptides; Quinoxalines; Rats; Rats, Inbred Lew; Retinal Ganglion Cells; Vaccination