Determination of the Best Concentration of Streptozotocin to Create a Diabetic Brain Using Histological Techniques.

Alzheimer's disease (AD) is one of the most important disorders among neurodegenerative diseases which is characterized by neurofibrillary tangles and senile plagues. Intercerebroventricular (ICV) streptozotocin administration is a form of sAD which was applied to examine different factors following AD. Previous reports used different doses of streptozotocin (STZ) to create Alzheimer's model, but no standard dose has been introduced. Therefore, we decided to investigate the best concentration of STZ to induce a diabetic brain with lowest mortality rate and high severity of destruction. We treated rats with three different doses of STZ (STZ 1.5, 2.25, and 3 mg/kg, ICV). Spatial memory for treated rats was evaluated by Morris water maze (MWM). Locomotor activities of rats were assessed by open field test. Histological observation such as immunohistochemistry, immunofluorescence, and Nissl staining were performed on the brain especially in CA1, CA3, and DG regions of hippocampal neurons at residues P-ser396 and P-ser404. Our data suggest that although the percentage hyperphosphorylation of tau protein by injection of STZ 3 mg/kg was about 10 % more than STZ 2.25 mg/kg compared to the control group, we considered the latter doses due to no effect on motor activities and enhance the number of glial cells.