title: Electroretinography in streptozotocin diabetic rats following acute intraocular pressure elevation.
abstract: BACKGROUND
  We consider whether pre-existing streptozotocin induced hyperglycemia in rats affects the ability of the eye to cope with a single episode of acute intraocular pressure (IOP) elevation.
  
  
  METHODS
  Electroretinogram (ERG) responses were measured (-6.08 to 1.92 log cd.s.m(-2)) in anaesthetized (60:5 mg/kg ketamine:xylazine) dark-adapted (>12 h) adult Sprague-Dawley rats 1 week after a single acute IOP elevation to 70 mmHg for 60 min. This was undertaken in rats treated 11 weeks earlier with streptozotocin (STZ, n = 12, 50 mg/kg at 6 weeks of age) or citrate buffer (n = 12). ERG responses were analyzed to derive an index of photoreceptor (a-wave), ON-bipolar (b-wave), amacrine (oscillatory potentials) and inner retinal (positive scotopic threshold response, pSTR) function.
  
  
  RESULTS
  One week following acute IOP elevation there was a significant reduction of the ganglion cell pSTR (-35 ± 11 %, P = 0.0161) in STZ-injected animals. In contrast the pSTR in citrate-injected animals was not significant changed (+16 ± 14 %). The negative component of the STR was unaffected by IOP elevation in either citrate or STZ-treated groups. Photoreceptoral (a-wave, citrate-control +4 ± 3 %, STZ +4 ± 5 %) and ON-bipolar cell (b-wave, control +4 ± 3 %, STZ +4 ± 5 %) mediated responses were not significantly affected by IOP elevation in either citrate- or STZ-injected rats. Finally, oscillatory potentials (citrate-control +8 ± 23 %, STZ +1 ± 17 %) were not reduced 1 week after IOP challenge.
  
  
  CONCLUSIONS
  The ganglion cell dominated pSTR was reduced following a single episode of IOP elevation in STZ diabetic, but not control rats. These data indicate that hyperglycemia renders the inner retina more susceptible to IOP elevation.
authors.affiliation: Department of Ophthalmology, Jikei University, 3-25-8, Nishi-Shimbashi, Minato-ku, Tokyo, 105-8461, Japan.
authors.forename: Kenichi
authors.initials: K
authors.lastname: Kohzaki
authors.forename: Algis J
authors.initials: AJ
authors.lastname: Vingrys
authors.forename: James A
authors.initials: JA
authors.lastname: Armitage
authors.forename: Bang V
authors.initials: BV
authors.lastname: Bui
mesh_terms: D000208:Acute Disease; D025042:Amacrine Cells / Q000502:physiology; D000818:Animals; D003623:Dark Adaptation; D003921:Diabetes Mellitus, Experimental / Q000503:physiopathology*; D004596:Electroretinography; D006943:Hyperglycemia / Q000503:physiopathology; D007429:Intraocular Pressure; D008297:Male; D009798:Ocular Hypertension / Q000503:physiopathology*; D020419:Photoreceptor Cells, Vertebrate / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012160:Retina / Q000503:physiopathology*; D051245:Retinal Bipolar Cells / Q000502:physiology; D012165:Retinal Ganglion Cells / Q000502:physiology*