Effect of insulin and L-ascorbic acid on rate of neuronal apoptosis in dentate gyrus and CA3 region of hippocampus in type 1 diabetic rats

Introduction: The aim of this study was to determine the effects of Insulin and Lascorbic acid on prevention of neuronal in granular layer of dentate gyrus and pyramidal layer of CA3 of hippocampus in streptozotocin-Induced diabetic rats. Methods: In this experimental study, diabetes type 1 was included by a single intraperitoneal injection of streptozotocin (STZ) (60mg/kg) in male adult wistar rats. After six weeks, STZ-injected rate were divided randomly into four groups as follow: (1) treated with Insulin (2) treated with Insulin + ascorbic acid (3) treated with ascorbic acid, and (4) untreated diabetic. After two weeks the brains were removed. Numerical density of TUNEL positive neurons in granular layer of the dentate gyrus and pyramidal layer were counted. Ultra structure of the injured neurons was studied. Results: Our findings showed diabetes type 1 caused Increased numerical density of TUNEL positive neurons in the dentate gyrus, pyramidal layer of CA3. Ultra structure showed server chromatin condensation, cytoplasmic radio-opacity and preserved nuclear membrane integrity indicative of apoptosis. In treated diabetic groups with Insulin, Insulin + ascorbic acid and ascorbic acid, numerical density of TUNEL positive neurons in the granular layer of the dentate gyrus and pyramidal layer of CA3 were lower than those of untreated group (P<0.001). Conclusion: It seems that, treatment of diabetic rats with insulin, ascorbic acid and combined treatment could prevent neuronal apoptosis.