Streptozotocin-induced Diabetes

All experiments were performed in accordance with the ARVO Statement for the Use of Animals in Ophthalmic and Vision Research. Male Long-Evans rats (180–200 g, six to seven weeks old) were obtained from Charles River Laboratory (Wilmington, MA). After 16 h of overnight fasting, diabetes was induced in each animal via intraperitoneal injection of 12 mg of streptozotocin (STZ, minimum 98%, HPLC, Sigma-Aldrich, St. Louis, MO) diluted in 0.2 ml of citrate buffer (0.1 M, pH = 4.5). Control animals received an intraperitoneal injection of vehicle (citrate buffer). Animals with blood glucose levels greater than 250 mg/dl at 24 h after STZ injection were considered diabetic. Body weights and blood glucose levels were regularly measured. Animals were maintained in an air-conditioned room under a 12-h light/dark cycle and were given free access to water and food.