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ABSTRACT
Background
Diabetes mellitus (DM) is a metabolic disorder that is caused by excessive glucose in the blood. It is projected that by the year 2040, 642 million people will be affected by DM. Experimentally induced DM alters hippocampal cellular and synaptic plasticity resulting in cognitive impairment. Streptozotocin (STZ) is regularly utilized to induce diabetes in drug development research that uses animal models of diabetes. The dosage of STZ and the length of time the animals are kept after induction of diabetes varies, with some studies using only 7 days and others for up to 60 days. The aim of this study was to investigate the effect of STZ-DM on hippocampal neuroanatomy in male Sprague Dawley rats observed for 21 days post DM induction.
Method
Brain tissues of 16 (8 normal and 8 STZ induced diabetic) Sprague Dawley rats were serially sectioned, slide mounted and stained with Crysil violet for volumetric and cell counts, and Giemsa stain for apoptotic cell counts in the hippocampus. Means of the above parameters were compared using SPSS.
Result
They were no significant difference in the volumes of granule cell layer (P=0,14), dentate gyrus (P=0,229) cornu ammonis (P=0,667) and pyramidal cell layer (P = 0,690) of the hippocampus. The neuronal cell count in dentate gyrus (DG) of the DM rats was significantly lower compared to the control rats (P =0,004). Apoptotic cells count in the DG was significantly higher in diabetic compared to normal rats (P=0,001).
Conclusion
STZ-induced diabetes did not affect the volumes of the hippocampus, but reduced neuronal cell count and increased apoptosis in a 21-day period. The effect of DM on the hippocampal neuronal cells could explain the observed cognitive impairment in DM patients. We conclude that DM affects the cells but not the volume of the hippocampus.