Benzodiazepine receptor agonist carbacetam modulates the level of vascular endothelial growth factor in the retina of rats with streptozotocin-induced diabetes

One of the primary mechanisms of retinal neurodegeneration in diabetes mellitus is gamma-aminobutyric acid (GABA) deficiency that makes the use of GABA-benzodiazepine receptor modulators a promising option for the correction of this diabetic complication. The aim of this study was to determine the effect of the benzodiazepine receptor agonist carbacetam on the expression of vascular endothelial growth factor (VEGF) and hypoxia-inducible factor-1α (HIF-1α) in retina of rats with hyperglycemia. Experimental diabetes was modeled by a single administration of streptozotocin (50 mg/kg) to three-month-old male Wistar rats. Immunoblotting and immunohistochemical studies were performed using monoclonal antibodies against VEGF and HIF-1α. It was shown that the development of diabetic retinopathy (DR) at the early stages was accompanied by a progressive multifold increase in the retina content of VEGF on 7-28 days and HIF-1α on 28th day. Insulin and insulin+carbacetam treatment significantly alleviated diabetes-induced overexpression of both HIF-1α and VEGF. Carbacetam was shown to block the diabetogenic increase in VEGF content in retina. The introduction of insulin with carbacetam significantly reduced the expression of VEGF and the development of specific morphological manifestations of DR. Thus, restoration of GABA-ergic signaling can be used as a promising therapeutic option for the correction of DR disorders. Keywords: carbacetam, GABA-benzodia­zepine receptors, HIF-1α hyperglycemia, retinopathy, streptozotocin-induced diabetes, VEGF