Changes in the Erg of Stz Induced Diabetic Rats and Its Utility to Detect Other Cerebral Alterations

Abstract

Purpose: : Diabetes also induces changes in retinal function; indeed, functional changes occur in the retina prior to clinical symptoms of the disease. The electroretinogram (ERG) has been used for decades to uncover the mechanisms of retinal physiology and their alterations in disease. The purpose of this work was to study changes in erg in a model of diabetes along time and to observe if these changes can be used to detect other cerebral alterations.

Methods: : Animals were treated in accordance to the ARVO statement for the use of animals in ophthalmic and vision research. Male, Wistar rats of approximately 60 days of age, corresponding to approx. 250 g body weight, at the beginning of the experiment, were used in the study. Diabetes was induced in animals by a single intraperitoneal injection of STZ (65 mg/ kg) in 0.1 M citrate buffer, pH 4.5.Fasting blood glucose levels were measured 72 h after STZ injection. Animals having blood glucose levels >200 mg/dL were considered diabetic. Animals were sacrificed after 2,5, 4 and 12 weeks of diabetes. Immediately before sacrifice erg, visual evoked potentials (VEP) and morris water maze were performed

Results: : Reduced b-wave amplitud and increased b-wave latenct time were detected as early as 2 weeks after diabetes induction. Increased in latency time in VEP were also detected after 12 weeks, moreover there was a positive correlation between b-wave latency and VEP latency time at this time point. Changes in morris water maze test were only detected after 12 weeks of diabetes.

Conclusions: : Changes in retinal function in diabetes occur prior to changes in hippocampus. These results suggest that further studies are needed to know if retinal functional tests can be used to monitorize other cerebral alterations in diabetic patients.

Keywords: diabetic retinopathy • electrophysiology: non-clinical • electroretinography: non-clinical