Effect of diabetes on median and dorsal raphe nuclei efferent fibers to CA3 hippocampal area in rat.

Diabetes Mellitus (DM) is one of the most important metabolic disease causes in many side effects. The decrease of mental abilities and even some form of dementia followed prolonged diabetes has been reported. There are evidences that show hippocampus might be the site of neural involvement in patients with dementia followed diabetes. As hippocampus received main serotonergic efferents from brain stem raphe nuclei include dorsal raphe nucleus (DRN) and median raphe nucleus (MRN), it is possible that these efferent affected by diabetes. We used adult male Wistar rat in this study. Diabetes was induced by i.p. injection of streptozotocin (STZ). After 2, 4 and 6 months, HRP tracing were done for the efferent from DRN & MRN to CA3 of hippocampus. HRP Positive neuron of DRN & MRN and also the distribution of these cells were study by light microscopy. Statistical analysis was done by SPSS software. Microscopic study clearly showed significant decrease in HRP positive cells population in DRN & MRN after prolonged diabetes. Based on our finding ,the changes in the neural connection between serotonergic nuclei and hippocampus followed diabetes might be one of the reasons for dementia in these patients.