title: Susceptibility of streptozotocin-induced diabetic rat retinal function and ocular blood flow to acute intraocular pressure challenge.
abstract: OBJECTIVE
  To consider the hypothesis that streptozotocin (STZ)-induced hyperglycemia renders rat retinal function and ocular blood flow more susceptible to acute IOP challenge.
  
  
  METHODS
  Retinal function (electroretinogram [ERG]) was measured during acute IOP challenge (10100 mm Hg, increments of 5 mm Hg, 3 minutes per step, vitreal cannulation) in adult Long-Evans rats (6 weeks old; citrate: n = 6, STZ: n = 10) 4 weeks after citrate buffer or STZ (65 mg/kg, blood glucose >15 mM) injection. At each IOP, dim and bright flash (-4.56, -1.72 log cd x s x m(-2)) ERG responses were recorded to measure inner retinal and ON-bipolar cell function, respectively. Ocular blood flow (laser Doppler flowmetry; citrate: n = 6, STZ: n = 10) was also measured during acute IOP challenge. Retinas were isolated for quantitative PCR analysis of nitric oxide synthase mRNA expression (endothelial, eNos; inducible, iNos; neuronal, nNos).
  
  
  RESULTS
  STZ-induced diabetes increased the susceptibility of inner retinal (IOP at 50% response, 60.1, CI: 57.0-62.0 mm Hg versus citrate: 67.5, CI: 62.1-72.4 mm Hg) and ON-bipolar cell function (STZ: 60.3, CI: 58.0-62.8 mm Hg versus citrate: 65.1, CI: 61.9-68.6 mm Hg) and ocular blood flow (43.9, CI: 40.8-46.8 versus citrate: 53.4, CI: 50.7-56.1 mm Hg) to IOP challenge. Citrate eyes showed elevated eNos mRNA (+49.7%) after IOP stress, an effect not found in STZ-diabetic eyes (-5.7%, P < 0.03). No difference was observed for iNos or nNos (P > 0.05) following IOP elevation.
  
  
  CONCLUSIONS
  STZ-induced diabetes increased functional susceptibility during acute IOP challenge. This functional vulnerability is associated with a reduced capacity for diabetic eyes to upregulate eNos expression and to autoregulate blood flow in response to stress.
authors: Department of Optometry and Vision Sciences, The University of Melbourne, Parkville, Victoria, Australia.
authors: Vickie H Y
authors: VH
authors: Wong
authors: Algis J
authors: AJ
authors: Vingrys
authors: Andrew I
authors: AI
authors: Jobling
authors: Bang V
authors: BV
authors: Bui
mesh_terms: D000818:Animals; D000903:Antibiotics, Antineoplastic; D003921:Diabetes Mellitus, Experimental / Q000139:chemically induced / Q000503:physiopathology*; D004195:Disease Models, Animal; D004198:Disease Susceptibility; D004596:Electroretinography; D005123:Eye / Q000098:blood supply*; D007429:Intraocular Pressure / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000378:metabolism; D009798:Ocular Hypertension / Q000503:physiopathology*; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D020318:Rats, Long-Evans; D012160:Retina / Q000201:enzymology / Q000503:physiopathology*; D013311:Streptozocin
chemical_list: D000903:Antibiotics, Antineoplastic; D012333:RNA, Messenger; D013311:Streptozocin; D019001:Nitric Oxide Synthase