title: Model of endothelin-1-induced chronic optic neuropathy in rat.
abstract: OBJECTIVE
  To describe a model of chronic endothelin (ET)-1 administration to the optic nerve and evaluate its effect on retinal ganglion cell (RGC) and axon survival in rat.
  
  
  METHODS
  Osmotic minipumps were surgically implanted in one eye of 113 Brown Norway rats to deliver 0.05, 0.10, 0.20, or 0.40 microg ET-1 per day (3.3, 6.7, 13.4, and 26.8 microM, respectively), or balanced salt solution (BSS) to the immediate retrobulbar optic nerve; the fellow untreated eye served as the control. Before pump implantation, RGCs were retrogradely labeled with fluorochrome. Animals were killed at 21, 42, or 84 days. RGC survival was expressed as the ratio of RGC counts in experimental versus control eyes in wholemounted retinas, whereas axon survival was expressed similarly from electron micrographs of the optic nerves. Serial optic disc changes were evaluated using scanning laser tomography. The effect of ET-1 (3 microL topical application of 10(-5) M) on blood flow in the surgically exposed optic nerve was measured using laser Doppler flowmetry in a separate group of five animals.
  
  
  RESULTS
  ET-1 led to a mean reduction in optic nerve blood flow of 68%. There were no significant differences in RGC survival among the four ET-1 doses used in this study. Pooled across all ET-1 doses, RGC survival decreased incrementally at 21, 42, and 84 days (P < 0.001; mean +/- SD, 0.77 +/- 0.25, 0.60 +/- 0.27, and 0.50 +/- 0.26, respectively) and was statistically significantly lower at each time point than in the BSS-treated animals. The axon survival data also showed a similar time-dependent loss. Only one of 21 animals showed significantly increased disc cupping, and there was no relationship between RGC survival and change in cupping. CONCLUSIONS. Chronic administration of ET-1 to the rat optic nerve results in a time-dependent loss of RGCs and their axons without apparent change in optic disc topography.
authors.affiliation: Retina and Optic Nerve Research Laboratory, Dalhousie University, Halifax, Nova Scotia, Canada. bal@dal.ca
authors.forename: Balwantray C
authors.initials: BC
authors.lastname: Chauhan
authors.forename: Terry L
authors.initials: TL
authors.lastname: LeVatte
authors.forename: Christine A
authors.initials: CA
authors.lastname: Jollimore
authors.forename: Paula K
authors.initials: PK
authors.lastname: Yu
authors.forename: Herbert A
authors.initials: HA
authors.lastname: Reitsamer
authors.forename: Melanie E M
authors.initials: ME
authors.lastname: Kelly
authors.forename: Dao-Yi
authors.initials: DY
authors.lastname: Yu
authors.forename: François
authors.initials: F
authors.lastname: Tremblay
authors.forename: Michele L
authors.initials: ML
authors.lastname: Archibald
mesh_terms: D000818:Animals; D001369:Axons / Q000187:drug effects* / Q000473:pathology; D002470:Cell Survival / Q000187:drug effects; D002908:Chronic Disease; D004195:Disease Models, Animal; D019332:Endothelin-1 / Q000494:pharmacology*; D015918:Infusion Pumps, Implantable; D017078:Laser-Doppler Flowmetry; D008297:Male; D009898:Optic Disk / Q000098:blood supply*; D009901:Optic Nerve Diseases / Q000209:etiology* / Q000503:physiopathology; D051381:Rats; D011914:Rats, Inbred BN; D012039:Regional Blood Flow / Q000187:drug effects; D012165:Retinal Ganglion Cells / Q000187:drug effects* / Q000473:pathology
chemical_list: D019332:Endothelin-1