The effect of chronic N(G)-nitro-L-arginine methyl ester (L-NAME) administration on visual evoked potentials and oxidative stress in streptozotocin induced diabetic rats

Abstract

Objective: The aim of this study was to investigate the effects of N(G)-nitro-L-argininemetyl-ester (L-NAME) on visual evoked potentials (VEPs) and oxidative stress in streptozotocin (STZ)-induced diabetic rats. Methods: Wistar rats were assigned to one of four groups: control (C), diabetic (D), control + L-NAME (CN) and diabetic + L-NAME (DN). Diabetes was induced by a single intraperitoneal injection of STZ (60 mg/kg). Three days after the STZ injection, diabetes was confirmed by measuring tail blood glucose concentration. L-NAME was injected intraperitoneally to the CN and DN groups at a dose of 10 mg/kg/d for eight weeks. VEPs were recorded by a photic stimulator. Thiobarbituric acid-reactive substance (TBARS) as an index of oxidative stress, and nitrite levels were measured fluorometrically in the brain and retina tissues. Results: L-NAME treatment produced a significant decrease in nitrite levels with respect to the control group, and body weight, water and food consumption and plasma glucose concentrations of the diabetic rats. TBARS concentrations were increased in diabetic rats. Although L-NAME treatment significantly increased the retina and brain TBARS levels in CN group, decreased TBARS concentrations were found in diabetic rats. All VEP components were significantly increased in diabetic rats. L-NAME caused a significant delay in all VEP components in CN group. Conclusion: Our results clearly showed that although L-NAME improved clinical manifestations of diabetes such as polyphagia, polydipsia, and also plasma glucose and TBARS concentrations in brain and retina tissues, it did not alter prolonged VEP latencies in diabetic state.