Effect of intracerebroventricularly injected streptozotocin on the cognitive performance of Long-Evans rats
Attila Gáspár1, Aliz Judit Ernyey1, Barbara Hutka1, Brigitta Tekla Tajti1, Bence Tamás Varga1, Zoltán Zádori1, István Gyertyán1
Brain insulin resistance is one of the molecular symptoms of Alzheimer's disease (AD). In rats, intracerebroventricularly injected streptozotocin causes insulin resistance and produces many symptoms of the human disease (cognitive decline, amyloid deposits, increase in phospho-tau). Our aim was to establish the model, which has exclusively been used with Wistar rats in the literature, in Long-Evans rats as well. Three months old male animals were treated with 2x1.5 mg/kg STZ or citrate buffer vehicle injected bilaterally into the lateral ventricles on days 1 and 3. Learning and memory capabilities of the rats were then tested in the following paradigms: five choice serial reaction time test (daily training, started from week 2 post surgery and lasting until the end of the experiment), novel object recognition test (at week 8), passive avoidance (at week 11) and Morris water-maze (at week 14). Besides, open-field activity (at 1 month) and elevated plus maze performance (at week 6) were also investigated. 15 weeks after the STZ treatment the animals were sacrificed and the brain phospho tau/tau protein ratio were determined by Western Blot technique. We couldn’t find any significant difference between the treated and the control groups in any of the assays, however, due to the low number of data (n=9 and n=8, respectively), no far-reaching conclusion can be drawn. Nevertheless, our findings suggest that the Long-Evans strain may be more resistant to the STZ treatment than the Wistar rats and higher doses are needed to trigger pathological changes in these animals.