Electroretinography in streptozotocin diabetic rats following acute intraocular pressure elevation

• Published in: Graefe's archive for clinical and experimental ophthalmology 2013-02, Vol.251 (2), p.529-535
• Main Authors: Kohzaki, Kenichi, Vingrys, Algis J., Armitage, James A., Bui, Bang V.
• Format: Article
• Language: English
• Subjects: Acute Disease; Amacrine Cells - physiology; Animals; Basic Science; Dark Adaptation; Diabetes Mellitus, Experimental - physiopathology; Electroretinography; Hyperglycemia - physiopathology; Intraocular Pressure; Male; Medicine; Medicine & Public Health; Ocular Hypertension - physiopathology; Ophthalmology; Photoreceptor Cells, Vertebrate - physiology; Rats; Rats, Sprague-Dawley; Retina - physiopathology; Retinal Bipolar Cells - physiology; Retinal Ganglion Cells - physiology
• ISSN: 0721-832X; 1435-702X
• DOI: 10.1007/s00417-012-2212-4

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.