Gabapentin protects against streptozotocin-induced diabetic retinopathy in rats: histological, immunohistochemical and ultrastructural study.

Diabetic retinopathy (DR) is a main cause of visual impairment globally. DR is mostly considered neurovascular degeneration. Gabapentin exerts antioxidant and anti-inflammatory effects. This study aimed to explore gabapentin's neuroprotective potential against DR. Forty-five adult male rats were divided into 3 groups; Control group I. Diabetic group II received an intraperitoneal dose of streptozotocin (STZ) (50 mg/kg) to induce diabetes. Blood glucose was assessed 48 h following STZ. Rats with blood glucose ≥ 250 mg/dl were considered diabetic. Gabapentin-treated diabetic group III in which the diabetic rats received gabapentin (300 mg/kg/12 h) by gastric tube. After 8 weeks, retinal samples were prepared for histological, immunohistochemical and ultrastructural studies. Diabetic group II revealed diminished cells of outer and inner nuclear layers, reduction in retinal thickness and ganglion cell number; and elevation of caspase-3 and Glial fibrillary acidic protein (GFAP) immune-expression and number of blood vessels expressing vascular endothelial growth factor. Disorganized discs of photoreceptors and neurons with shrunken nuclei were found. Gabapentin-treated diabetic group III showed preserved histology and ultrastructure and reduction in caspase-3 and GFAP immune-expression and number of blood vessels. In conclusion, gabapentin has neuroprotective potential against DR and might represent a valuable therapeutic tool in the future.