Evaluation of the Effects of Recurrent Dexmedetomidine on Cognitive Functions and Brain Tissue in Streptozotocin-Induced Rats with Alzheimer's Disease

Abstract

Objective: The aim of this study was to evaluate the effects of recurrent dexmedetomidine on cognitive functions and brain histopathology in the elderly rat model which has Alzheimer disease created with streptozocin (STZ).

Materials and Methods: Totally 24 aged Wistar Albino rats were divided into 4 equal groups; control (Group C), sham (Group S), Alzheimer (Group A) and Alzheimer + dexmedetomidine (Group AD). All rats in Group A and Group AD received stereotaxic injection under ketamine (100 mg / kg, i.p.) anesthesia. Midline burr hole was entered under the dura. Group A and Group AD 3 mg/kg (10 ml) were induced by administering STZ experimental Alzheimer intracerebroventricularly. Four weeks after the surgery, Group S and Group AD received 100 µg/kg (i.p) dexmedetomidine for 3 consecutive days. Each group were tested with RAM test. After 24 hours, all rats were euthanized under anesthesia and brain tissue was taken. Hippocampus tissues were evaluated Biochemical and histopathologically.

Results: At the beginning, the number of The radial arm maze test (RAM) input-output is similar in all groups, but 3 weeks after the Alzheimer's formation RAM input-output decreased significantly. In Group AD, the number of RAM input-outputs increased significantly compared to Group A after 2nd and 3rd anesthesia applications. Glial fibrillary acidic protein levels were significantly higher in Group A compared to C and S groups in hippocampus tissue. In Group AD, it was found to be significantly lower than Group A. In group A Catalase (CAT) and Paraoxonase 1 (PON-1) activities and Thiobarbituric acid reactive substances (TBARS) level of brain tissue were found higher than Group C and S. TBARS levels of Group AD brain tissue was significantly lower than Group A.

Conclusion: We concluded that recurrent dexmedetomidine administration in rats treated with STZ positively affects cognitive functions evaluated with RAM in the presence of recurrent dexmedetomidine. Also histopathological and biochemical markers supported these findings. We concluded that observational studies should be performed in large series to correlate these results with clinical applications.