In addition to cognitive deficit, diabetes may also causes neuronal loss in different areas of the brain specially hippocampus. The aim of the present study was to investigate the effects of type I (T1D) and type II (T2D) diabetes on cognitive function and hippocampal neuronal density in rat. Three groups of male Wistar rats (n=7) assigned as follows; control, T1D and T2D. T1D was induced by chemical surgery and T2D was induced by 10% fructose treatment through drinking water. Two months after the induction of both types of diabetes the learning abilities and memory retention of animals were measured (Morris Water Maze and shuttle box). After that all animals were perfused and their brains processed for stereological estimation of neuronal density in hippocampus. In parallel to significant decrease in learning and memory scores, T1D showed a meaningful reduction in hippocampal neuronal density, when compared to control group. In T2D, the reductions of cognitive scores as well as hippocampal neuronal density were not significant, when compared to control and T1D. Although both types of diabetes can lead to neuronal loss and cognitive dysfunction, these abnormalities were more obvious in T1D. Similar abnormalities in T2D are probably age-related and will be manifested more obvious in aged animals.

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