Background: Diabetes is one of metabolic disorders characterized by hyperglycemia due to defects in insulin secretion, insulin function, or both. Diabetes induces neuronal death in different regions of the brain especially hippocampus. In this regard, the present study has been conducted to compare the effects of type I and type II diabetes on hippocampal neuronal density in Wistar rat. Methods: Male Wistar rats were divided into three groups including control, type 1 and type 2 diabetes. Type I diabetes was induced by a single subcutaneous injection of Alloxan (135 mg/kg body weight), and for type 2 diabetes, drinking water containing 10% fructose was administered for eight weeks. Two months after diabetes confirmation, hippocampal neuronal density was investigated using dissector technique. Results: Neuronal density in CA1 region showed significant decrease in both experimental groups compared to control, whereas CA3 neuronal density demonstrated a remarkable reduction only in type 1 diabetic group in comparison with control (P<0.05). Likewise, in the whole hippocampus, there was a statistically meaningful difference between control and type 1 diabetic group (P<0.05). Conclusion: Significant reduction in CA1 neuronal density may be possibly due to more vulnerability of this region to pathological conditions. In the whole hippocampus, decrement in neuronal density was also more significant in type 1 diabetes, while in type 2, neuronal density could be associated with age and diabetes duration.

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