Evaluation of novel object recognition test results of rats injected with intracerebroventricular streptozocin to develop Alzheimer's disease models

It is challenging to create chemical-induced models of Alzheimer’s disease without using genetically bred animals. Intracerebroventricular (ICV) streptozocin (STZ) administration at a sub-diabetogenic dose can serve as a viable model for cognitive impairment associated with Alzheimer's disease via a disruption of glucose and energy metabolism in the brain, accompanied by oxidative stress and a concurrent impact on cognitive function. The aim of this study is to evaluate the behavioral results of once or twice injections of the ICV STZ administration methods. ICV guide cannulas were placed unilaterally on 20 Wistar adult female rats using stereotaxic surgery. Rats divided into 4 groups were given a single dose of vehicle or STZ (3 mg/kg) once and twice (2 doses with an interval of 72 hours). Novel object recognition tests were conducted two weeks after the first injection. Recognition and discrimination indexes for short-term and long-term memories were calculated and analyzed with ordinary one-way ANOVA and post-hoc Tukey tests on GraphPad-Prism 9.1.2. The animals given STZ twice showed a statistically significant decline in recognition and discrimination indexes in short-term memory. However, no difference was found in animals given a single dose of STZ. Both groups showed a significant decrease in the indexes evaluating long-term memory compared to the control group (p<0.05). There are conflicting results in the literature regarding the use of STZ models in female rats. Our study found that administering STZ twice was more effective in evaluating short-term memory than a single administration.